You need to add dimension to it. The whole room is flat. You have a slanted view looking into the room with the wall on the bottom need to keep up the consistancy and put a wall on the top part as well other wise the level looks like its on top of a box or something if you get what I mean. But if you added a wall to the top it would look like you're inside it.
Another thing just my personal opinion but I dont think those blue pillar tiles you used match the color theme of the rest of the level. I would rething it with something that matches the rest of the level better.