well... assuming you're doing a still shots... perhaps you should decide how the camera is going to point and where the light is going to be in those shots

then render off a picture for each building you think would be in the scene then go to your paint program and slap them together

if buildings have shadows cast on them from other buildings then you could just paint them in or import the building into the scene and render off.

well... sounds like you probably already considered that though, so whatever your solution i hope you get something decent