In the Sound Room, you mentioned being concerned about Rocket Rise being monotonous, and during my playthrough, I did start to feel that way about it. What do you think about using The Road Warrior for the cloud-tileset levels instead, leaving Rocket Rise for the skybase-tileset levels? I think it would work nicely for those levels as well as use a previously unused track. At the very least, I think it would fit Very Long Fall in particular.
EDIT: Speaking of Very Long Fall, there's a hole in the bottom-right wall that's plugged by an invisible wall, but previous levels have taught players that they can jump into those gaps by holding down to duck. This means the fake gap implies a secret area but is actually a cheap hit. Please plug the gap with regular, visible solid tiles instead.