Not bad for a first attempt in a while so I'll be a little lenient.
- The walls don't seem right, and it looks even more awkward with the doorways.
- The castle pillar I don't like being right there in front of a doorway. Those can get bothersome when walking into a level for the first time and getting trapped, or not realizing you're walking into a blocked path.
- On the bottom left and right corners they seem to be missing something. Probably would look nice with some statues or other objects up on them.
The walls are really what bug me the most though. Something about them.