I've been playing around with an idea to make quick organic believable city layouts and think I'm onto something - I thought I'd share. I've only just started using this method but think it shows promise. It's a bit obvious so my apologies if it is just a repetition of basics:

Here is what I have so far:

How I did it.

Open CC2 and start with a blank background.
Import a bitmap of a any medieval city map (I used York) and put it on its own layer.

Make a new layer ('roads') and using the 'smooth path' tool, draw curves following the centres of the roads.

Hide the bitmap layer. Then select city/random street (you may want to set the parameters of the houses using city/random street options first) and lay down streets by clicking on the road paths you have already laid down. Tip: if the house at the end of the path is the wrong shape/size, back up with the mouse and go forward again, it will put in a different random house.

Clean up by adding / deleting / resizing / repositioning and rotating individual houses.

Making the image above took about 20 minutes. It needs more cleaning up but I think you can see the idea.