There's a good chance you already know about this, but there's a lot of city textures that come with Counter-Strike. You could also try downloading other mods, and taking textures from them (The Specialists would be a good place to start).
If you still can't find any, try making your own from pictures. It's really not all that hard. And if you don't feel like going out and taking yor own pictures, there's plenty of good free texture/picture resources out there, like this one:
http://www.mayang.com/textures/