How to use the following interface in wince 6.0 r3 for implementing hardware acceleration for graphics in silverlight
You can find here a Guide how to implement the Hardware acceleration for Silverlight in WEC7. http://msdn.microsoft.com/en-us/library/jj919286.aspx
(I recommend to use Windows Embedded 7 for Silverlight if possible, Microsoft did quite some improvements compared to wince 6.0 r3)
Alternative you can also use a module which proivdes the HW acceleration out of the box. Here a video which shows the differenc with enable/disable HW acceleration: http://developer.toradex.com/knowledge-base/microsoft-silverlight
If you mainly want to have a fancy 3D User interface, take also a look at the Nvidia UI Composer which is available for Win CE 6 too.