It's going to be hard to make a town look like a mash-up at icon size. The only thing that you can try is to draw some buildings out by hand at a large size, stick em together, and then shrink it down to fit the space. Shrinking it down will kill a bunch of the detail, though. So you're in a catch-22. The best way to convey that mash-up feel is to do an ISO city map and just put some dots and squares on this one. You could do your city map as an inset map on this one and thus combine everything into one image.