The last source code release I did for the web part was buggy.
Sorry part of the joy of web part dev and cached items and everything else that goes with it.
Also I took the time to migrate the code to codeplex the initial release has the bug fixes and enhancements to select different image library lists from the site, this was the reason it was based on the template part so that many of the parts will work together. The picture show 3 parts using different lists.
All source code and a place to suggest things can now be found here.
and btw codeplex rocks.
Binary Jam 
How do you code for the pictures to be pulled from a SharePoint Library?
All the code is there for you to see. Visit Codeplex and just download the code.
But basically you iterate the SPList collection for the URL’s and Silverlight downloads the pictures via the URL’s supplied, a big array in client side Jscript is created for thumbnails and medium sized piccys.