I'm building an app that generates a grid of HubTile objects from the Silverlight Toolkit representing people, with the Source property being set to a URL for their profile picture that's returned from a web service. If the person hasn't uploaded a profile picture, the URL that's returned is a GIF for a generic profile picture. It appears that the HubTile simply ignores the Source, because the image isn't being displayed. I've verified that the image exists at the provided URL. Are GIF's simply an unsupported image type for the HubTile? Unfortunately, the documentation on Codeplex is empty.
No, GIF images are not supported. From "Tiles Overview for Windows Phone":
Tile images can be either a .jpg or .png file
If you are referring to the HubTile control, it uses an Image under the hood which does not support GIFs either. As per Supported Media Codecs for Windows Phone
This file type [GIF] is unsupported by the Silverlight Image element