"How to Optimizing SharePoint Picture Library for Use with the Content Rotator", this question was asked a few times by customers of ours. We have created a guidance about this and published it on our documentation : 

https://help.infragistics.com/Doc/SharePoint/2012.1/CLR4.0?page=SharePoint_Content_Rotator_Optimize_Picture_Library_for_Use_with_the_Content_Rotator.html

Hope this helps!