50D and digital frames...
All digital frames have very LOW resolution. You should crop your photos to its native aspect ratio, resize it to the exact dimension and sharpen it. You end up with smaller file sizes that allow you to put more photos in the frame.
IMHO, all digital frames, with their lousy resolutions, are over priced. They will not do justice to your 15M 50D photos.
For a little more, you can get a cheap laptop with 1280x800 pixels that can act as a digital frame (think screen saver) and do a lot more. Most digital frames are bought as gifts to grandparents with poor eye sight.