This isn't a "fix" or anything, just an idea. I'm not sure how you would interact with these images (zoom, etc), but it would be very helpful to be able to place images around the canvas in the actual workspace background. Especially when you're in full screen mode, with the gray area stretching all the way to the edges. This would be a great asset to people using the program from illustration, and would give the feel of actually taping up reference around the artwork. That area isn't used for much at the moment. I'm surprised Adobe hasn't utilized it as a kind of "behind the canvas" pinboard or color mixer or something.
Not an un-interesting proposal – though I wonder what it would mean programming-effort- and file-size-wise.
Personally I’d rather see a feature like »layer as guide« where a Layer’s pixel content on the canvas can be kept visible while working in Photoshop but would appear neither in the Preview and flattened copies nor be accessible in layout applications.