Sorry Moe, I forgot to answer your question yesterday:
No, I don't know exactly how many buildings I have. But I came to the conclusion that it won't be too far from the 20,000 to 45,000 inhabitants which were my goal After a rough estimation I'd say i drew about 6000 buildings.
Thank you, Yandor, but I don't think that would help - great idea, though, maybe I can use it nex time! I first draw the trees (just a stroke, as I use scattering etc.) and then fill the gaps with varying colors. It's just so boring doing it over and over again