Try mixing in some other kind of stairs as well? You can also throw some leaves on them and hang them off the side.
I honestly don't think making the roofs of the buildings more detailed would really make a difference. When you're playing the map, a lot of the buildings are too tall to actually see the roofs, so it isn't much of an issue. I personally prefer the roofs simple like that because it's a nice contrast to the detailed sides.
Anyway, this map is probably one of the best I've ever had the opportunity to see (no bias). Andrew and the rest of the helpers really worked hard on this map, and the finished product just blows me away every time I hop on the server and look around. I sincerely hope this map gets added onto the servers, as I can assure you, even though the islands look relatively small in the screenshots, there's PLENTY of flat land to PVP on.
Nice work Andrew <3