You're not stopping entirely with castles, are you!?
Like all MOCs, buildings need life around it to not look like some prop (plus, the pic is of a rather low quality*). It seems a bit lifeless in the picture you've posted, but I saw Quarryman's pictures of it
at last weekend's exhibition and it looks far better there, when it is in its right enviroment. This is always the key to a good MOC, IMO: Life. You were good at it with your castles, and its understandable that it can be hard to incorporate when you're not used to City MOCs. But it'll come to you.
You're off to a good start, my friend.
* - Just found out why, and you're not to blame. ;) Still, the all-white background effect is recommended if possible.
Edited by Freddie, 01 April 2009 - 11:44 PM.