Thanks for the sample, but yeah, those "GravityZone"-like sprites wouldn't really be possible in my case since the playing field is dynamic.
In regards to your questions: the speed of the objects is set to about 60, but they could go as fast as ~250ish. They should be reasonably close to the surface (within 5-10 pixels). The objects are about 24x24 pixels, whereas the rest of the tiles are 32x32. They don't necessarily need to rotate as they go around corners. The new landforms appear out of thin air (you create them by clicking). Finally, the objects are held down by gravity (when they're on the floor; when they're following the ceiling, the gravity is set to 0).
If you (or anyone else) can think of anything that might work with that information, I'm all ears. Thanks again.