Oh hey, two cool ideas for levels which wouldn't need shading:
Frogger 2: Swampy's Revenge: Super Retro Levels-
Playing on the road or side-walks, while different cars, turtles and logs pass down the screen in both directions. The camera would have to be angled downwards if possible, or 3D models of the different objects would have to be made or
found online. I could help with that if you're willing to make it...
This stage would fit into Brawl due to its fast and periodical nature (Onett, Wario Ware Inc.), and would be easy to develop (everything moving hurts you on contact, the stage is flat.)
DOOM: Any level-
A fight amongst MIDI-metal music in a grimy atmosphere, while bill-boarded 2D enemies shoot from both sides of the stage every 30 seconds or so. I could supply 3D conversions of levels.
DOOM is a cult classic, and it'd be an interesting and totally new look for a stage.
...Not that they are requests. You're just the only one who was game enough to release imported levels so far.