I haven't tried it personally, and it does come with a price, but have you looked at profantasy software's Campaign Cartographer? One of their products, City Designer, may have what you're looking for: <a href="http://www.profantasy.com/products/cd3_detail.asp" rel="nofollow">http://www.profantasy.com/products/cd3_detail.asp</a>
Again with a price is also dundjinni which may actually have some better building/city item renders: <a href="http://www.dundjinni.com/" rel="nofollow">http://www.dundjinni.com/</a>
I've noticed in my mapmaking in roll20 that a lot of the higher-res and even photorealistic (to some degree) items have been from dundjinni.com. I don't think I'd quite use that high of detail for a larger scale map though :P.
That's what I know; hope it helps a bit.