I'm not sure what the mosaic settings in Photoshop are.
I have attached the Gimp dialog. I found the best effect was as selected (for buildings.
map1.png
I also did a quick test running the mosaic filter three times. Also attached. Think I'll keep playing as there seems some potential for filling large areas easily. There has to be a reasonable programmatic way to generate streets.... might have to look into L-systems and fractals again
-Rob A>