with definable range of motion mappable to the mouse cursor, so you could have a scene that moves or spins slightly as the cursor moves around the screen in other apps.
sure, i can imagine it would be tricky, and probably a nightmare of compatibility problems, but how cool would that be?
i'd waste some gpu cycles on that while i was doing non-graphic intensive work 
Hmm some sort of half 3d, hdri destkop solution. Maybe that exists already somewhere.
i don't think you'd need to really have it in real 3d, i mean there is this sort of fake 3d on facebook currently with a single image. Pretty sure that could be somehow used.
Personally i like my calming Armageddon style underwater wallpaper filled with all my desktop apps. More animation would probably get on my nerves at some point 
Try rainmeter app for customizing your desktop background and it has lots of cool skins.
see this list of latest themes: https://techiespad.com/rainmeter-skins/
