It looks really promising, but in the picture I can see two small mistakes:
There's missing wall behind the doors.
One tile on the ceiling is flat.
You also should put black outlined grass everywhere, even in front of the stone (if the stone is not layer 3, it could be done with using more background layers).
It will make your level look more "professional". For me, there is nothing worse than nice, playable level full of SGEs.