Your cliffs are incorrectly made I can't make them correctly though so I shouldn't be talking. You also forgot the corner tiles on the roof. You may also want to work on the placement of the objects. Also for a more complex feel try using the silvery tiles with the brown ones to provide variation. Try using the laying down barrels and if you post the actual level I may give you some examples though i can't exactly give a good one. And generally all the bases have tiles around them surrounded by that border thing. Try walking around on artic and other levels for an example.Also the thickness should be the same on the base height or else it would be slanting and we would fall of

. Please post the NW and I will try to show you what I mean because I understand im very unclear

Im just trying to help with suggestions though I may not be a good person to give the examples etc... What you should think is how would this look as compared to the normal zone stuff. Other than that it looks great!
Edit: I tryed to give an example but all my levels were messed up.