The pallete for Marble Zone and for Labyrinth Zones look good. Spring Yard Zone isn't half-bad either, but Green Hill Zone...too much green man. As I tell a lot of people...you should consider trying to put in new art, even if its something that's just a tweak on the existing art rather than a full-blown overhaul. The GHZ and SLZ edits on Aka Mekon's hack are the best examples of what I mean. Done right, just amending the existing art can add a whole new feeling to a level.