Icons used by Silverlight OoB solutions have to be .PNG files. There are at most 4 icons with the sizes 16x16, 32x32, 48x48 and 128x128.
The source types to select from are:
- .PNG files that are already included in the .XAP file
- .PNG files placed somewhere on disk that will be included in the .XAP file at build time
Silverlight environment will choose the best icon for each usage. For example the small icon displayed in the title bar of the application window when using single border style, shortcuts, etc.