By default, an MdiTab will only display an image if one is specified on one of the tab appearances (TabAppearance, SelectedTabAppearance, etc.). To have the tab display the Icon of the associated Form, set the DisplayForm icon property to true.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2