Looks pretty good I would echo geamon about the walls. I use the rectangle tool to start and once I find a width that I like I copy and paste sections of it to make my walls. (maybe a bit tedious and layer heavy but it ensures all my walls are the same width and I can merge all the layers down after the walls are up) I personally like your colors there becoming your "style", and IMO for these types of map the better you can see things well..the better