Jegol: The lightening you did works well; I'd go just an inch or two further with it.

As for adding the buildings, I would suggest creating a custom brush exactly in the method described in the first post of my mosaic tile map tutorial except let the size jitter a bit more and lower the angle jitter. This will produce the same effect in PS that Redrobes describes was in RobA's Gimp tutorial. Don't forget that you can always select a bunch of buildings you already have, use the Move tool with the alt button down, and a copy will be made for you. (You can also ctrl-T to transform it, flip it, change the size, etc.) I think it will not take long to add more buildings at all.

Looking good, though! Make sure to post the next edit!