[Cid_Night]

well...it needs some work, the walls are kind ugly, u could use those tiles but be more careful about placing them and make sure they fit together right and dont come out looking like they...im not sure the word im looking for but basically they dont look like they're placed together right, even with the "rough look" you were going for.
-edit-
also at the top of your waterfall system, find a better tile for it to come out of besides just black, or something to outline the black so it doesnt just look like a black rectangle with water under it.