My Silverlight app was referencing an external assembly, called Library.Resources.dll, which contained some images. When I set my UriSource to UriSource="/Library.Common;Component/Images/view.png" my image appeared at design time without any problem. However, when I ran the application the image would not appear.

After inspecting the contents of my XAP file I noticed that the resource assembly was missing. Apparently, assembly’s ending in Resource.dll are not allowed in the XAP which was why mine was missing. I changed the name of the assembly to Library.Common, as well as my UriSource then the assembly was included in the XAP file and and my images successfully appeared.