Too lazy to check if this was posted already, but how about taking snapshots or uploading pictures onto your SD card to decide what your custom stage background will be like? Oh, and a moving-stage-styled custom stage would be nice too. Port Town, Delfino, or even Rumble Falls-style would be nice. You get to create the mobile platform that moves around on each small stage you make with your blocks, and even an infinite stage that keeps scrolling up (but no one would make a stupid stage like rumble falls

).