i modified your sample project to use a StackPanel inside the first row of the grid, so you can just add timelines to it repeatedly and you should see them all in the end.

as for making the Scene white, i think you just need to set the timeline's Background property.

<UserControl x:Class="SilverlightApplication35.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:igTimeline="clr-namespace:Infragistics.Silverlight.Timeline;assembly=Infragistics.Silverlight.DataVisualization.Timeline.v9.2"
             xmlns:igControls="clr-namespace:Infragistics.Silverlight.Controls;assembly=Infragistics.Silverlight.DataVisualization.Controls.v9.2"
     Loaded="UserControl_Loaded">
    <UserControl.Resources>
        <Style x:Key="PaneStyle1" TargetType="igTimeline:Mark">
            <Setter Property="Height" Value="3"/>
            <Setter Property="Stroke" Value="Black"/>
            <Setter Property="Fill" Value="Black"/>
            <Setter Property="VerticalAlignment" Value="Top"/>
        </Style>
        <Style x:Key="MinorTickMarkStyle1" TargetType="igTimeline:Mark">
            <Setter Property="Width" Value="2"/>
            <Setter Property="Height" Value="12"/>
            <Setter Property="Stroke" Value="Black"/>
        </Style>
        <Style x:Key="LegendStyle1" TargetType="igTimeline:Legend">
            <Setter Property="Visibility" Value="Collapsed"/>
        </Style>
        <Style x:Key="EventPointStyle1" TargetType="igTimeline:EventPoint">
            <Setter Property="Width" Value="8" />
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="igTimeline:EventPoint">
                        <Grid>
                            <Rectangle Fill="{TemplateBinding Fill}" Stroke="{TemplateBinding Stroke}" Height="15" Width="8"></Rectangle>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <Style x:Key="EventTitleStyle1" TargetType="igTimeline:EventTitle">
            <Setter Property="Visibility" Value="Collapsed" />
        </Style>
        <Style x:Key="TimelineStyle1" TargetType="igTimeline:XamWebTimeline">
            <Setter Property="Visibility" Value="Collapsed" />
        </Style>
        <Style x:Key="SceneStyle1" TargetType="igTimeline:Scene">
            <Setter Property="Background" Value="White"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="igTimeline:Scene">
                        <Grid>
                            <igTimeline:GridArea x:Name="GridAreaElement" />
                            <Grid Style="{TemplateBinding SceneGridStyle}">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="0" />
                                    <RowDefinition Height="Auto" />
                                    <RowDefinition Height="0" />
                                    <!--set the height to 0-->
                                </Grid.RowDefinitions>
                                <igTimeline:SeriesPane x:Name="SeriesPaneTopElement" />
                                <Grid x:Name="AxisPaneElement"  Height="50" Grid.Row="1"></Grid>
                                <igTimeline:SeriesPane x:Name="SeriesPaneBottomElement" Grid.Row="2" />
                            </Grid>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Resources>
    <Grid x:Name="LayoutRoot" Background="White">
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition Height="60" />
        </Grid.RowDefinitions>
        <igControls:XamWebZoombar Background="White" x:Name="Zoombar" ZoomChanged="Zoombar_ZoomChanged" Margin="0,0,44,15" Height="41" VerticalAlignment="Bottom" Grid.Row="1">
        </igControls:XamWebZoombar>
    </Grid>
</UserControl>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Infragistics.Silverlight.Timeline;
using Infragistics.Silverlight.Controls;

namespace SilverlightApplication35
{
    public partial class MainPage : UserControl
    {
        TimelineEntity timeLineEntity = null;

        DateTimeAxis axis = null;
        public MainPage()
        {
            InitializeComponent();
            LoadData();
            axis = new DateTimeAxis()
            {
                Minimum = timeLineEntity.StartTime,
                Maximum = timeLineEntity.EndTime,
                AutoRange = true,
                Unit = 2,
                UnitType = DateTimeUnitType.Seconds,
                ShowLabels = false,
                ShowMinorGridLines = false,
                ShowMajorTickMarks = false,
                ShowLabelsInPreview = false,
                ShowMinorTickMarks = false,
                ShowThumb = false
            };

            int i = 0;
            StackPanel timeLineStack = new StackPanel();
            foreach (Events eventItem in timeLineEntity.EventList)
            {
                XamWebTimeline timeline1 = new XamWebTimeline();
                DateTimeSeries timeSeries = new DateTimeSeries();
                DateTimeAxis subaxis = new DateTimeAxis()
                {
                    Minimum = eventItem.StartTime,
                    Maximum = eventItem.EndTime,
                    AutoRange = true,
                    Unit = 2,
                    UnitType = DateTimeUnitType.Seconds,
                    ShowLabels = false,
                    ShowMinorGridLines = false,
                    ShowMajorTickMarks = false,
                    ShowLabelsInPreview = false,
                    ShowMinorTickMarks = false,
                    ShowThumb = false
                };
                timeline1.Axis = subaxis;

                foreach (DateTime marker in eventItem.Markers)
                {
                    DateTimeEntry entry = new DateTimeEntry();
                    entry.Time = eventItem.Markers[0];

                    entry.Title = "Marker in Event";
                    entry.Details = "";

                    timeSeries.Entries.Add(entry);
                }

                timeline1.Series.Add(timeSeries);

                i++;

                timeline1.VerticalContentAlignment = VerticalAlignment.Top;

                timeLineStack.Children.Add(timeline1);
            }
            this.LayoutRoot.Children.Add(timeLineStack);
        }
        private void LoadData()
        {
            timeLineEntity = new TimelineEntity();
            timeLineEntity.StartTime = Convert.ToDateTime("08/01/2009 12:00:00");
            timeLineEntity.EndTime = Convert.ToDateTime("08/11/2009 13:30:00");
            timeLineEntity.Title = "Event Time Line";
            string[] startDate = new string[5];
            startDate[0] = "08/01/2009 12:00:00";
            startDate[1] = "08/01/2009 12:10:00";
            startDate[2] = "08/04/2009 13:30:00";
            startDate[3] = "08/06/2009 06:30:00";
            startDate[4] = "08/08/2009 04:30:00";
            string[] endDate = new string[5];
            endDate[0] = "08/02/2009 13:30:00";
            endDate[1] = "08/04/2009 10:30:00";
            endDate[2] = "08/04/2009 13:40:00";
            endDate[3] = "08/06/2009 07:30:00";
            endDate[4] = "08/08/2009 13:30:00";
            string[] markerstartDate = new string[5];
            markerstartDate[0] = "08/01/2009 13:30:00";
            markerstartDate[1] = "08/03/2009 13:30:00";
            markerstartDate[2] = "08/04/2009 13:35:00";
            markerstartDate[3] = "08/06/2009 06:40:00";
            markerstartDate[4] = "08/08/2009 07:00:10";
            List<Events> eventList = new List<Events>();
            for (int i = 0; i < 5; i++)
            {

                Events eventItem = new Events();
                eventItem.Title = "Event #" + (i + 1).ToString() + " Event Type";
                eventItem.StartTime = Convert.ToDateTime(startDate[i]);
                eventItem.EndTime = Convert.ToDateTime(endDate[i]);
                List<DateTime> markers = new List<DateTime>();
                markers.Add(Convert.ToDateTime(markerstartDate[i]));
                eventItem.Markers = markers;
                eventList.Add(eventItem);

            }
            timeLineEntity.EventList = eventList;
        }
        private void Zoombar_ZoomChanged(object sender, ZoomChangedEventArgs e)
        {
            List<XamWebTimeline> timelines = new List<XamWebTimeline>();
            this.GetTimelines(this.LayoutRoot.Children, timelines);
            foreach (XamWebTimeline timeline in timelines)
            {
                timeline.Axis.ScrollPosition = e.NewRange.Scroll;
                timeline.Axis.ScrollScale = e.NewRange.Scale;
            }
        }
        private void GetTimelines(UIElementCollection elements, List<XamWebTimeline> result)
        {
            foreach (UIElement ctrl in elements)
            {
                if (ctrl is XamWebTimeline)
                {
                    result.Add((XamWebTimeline)ctrl);
                }
                else if (ctrl is Panel)
                {
                    this.GetTimelines(((Panel)ctrl).Children, result);
                }
            }
        }


        private void UserControl_Loaded(object sender, RoutedEventArgs e)
        {
            List<XamWebTimeline> timelines = new List<XamWebTimeline>();
            this.GetTimelines(this.LayoutRoot.Children, timelines);
            foreach (XamWebTimeline timeline in timelines)
            {
                timeline.Background = new SolidColorBrush(Colors.White);
                if (timeline.Zoombar != null)
                {
                    timeline.Zoombar.Visibility = Visibility.Collapsed;
                }
                timeline.Axis.PaneStyle = (Style)this.Resources["PaneStyle1"];
                timeline.Axis.VerticalContentAlignment = VerticalAlignment.Top;
                timeline.LegendStyle = (Style)this.Resources["LegendStyle1"];

                timeline.SceneStyle = (Style)this.Resources["SceneStyle1"];

                foreach (DateTimeSeries series in timeline.Series)
                {

                    series.EventPointStyle = (Style)this.Resources["EventPointStyle1"];
                    series.EventTitleStyle = (Style)this.Resources["EventTitleStyle1"];
                    series.EventSpanStyle = (Style)this.Resources["EventSpan1Style"];
                }
            }

            Zoombar.Range.FromScaleScroll(axis.ScrollScale, axis.ScrollPosition);

        }
    }
    public class TimelineEntity
    {
        public string Title { get; set; }
        public DateTime StartTime { get; set; }
        public DateTime EndTime { get; set; }
        public List<Events> EventList { get; set; }
    }
    public class Events
    {
        public string Title { get; set; }
        public DateTime StartTime { get; set; }
        public DateTime EndTime { get; set; }
        public List<DateTime> Markers { get; set; }
    }
}