The AC unit looks great. My only criticism is that wire doesn't look too great. Not much else to comment on until it's put into the scene. Depending on how high up the roof is you could do some pretty cool stuff with the skybox. Here's a shot of the skybox from No Mercy in Left 4 Dead. It's mainly just a mixture of very lowpoly buildings, building cards and mountain cards. If you're interested in doing something like that I could grab you some better screenshots of that skybox and get some wireframes of them.