@schroedl: The natvis description requires a pointer to the pixel data, which is not immediately accessibly with opaque handles like HBITMAP. That said, you can write natvis descriptions for the corresponding "locked" structures, e.g. BitmapData. We are currently working on a mechanism for supporting opaque types, but these are a bit tricky since you potentially need to run code in your app to get at the pixels.
@daniel z: You can view your own image types; details are described here. Regarding your second question, Image Watch does not play videos, but you can view individual frames as long as they are in a supported format (uncompressed interleaved 8bit RGB, for example).