Cityscape script

This is my first posting here … Hello everyone !

In order to improve a previously completed scene, I am currently working on a cityscape generation script. Here are a few examples of its output:

http://www.uploadgeek.com/thumb-75FF_4A8C3C09.jpg

http://www.uploadgeek.com/thumb-8DD9_4A8C3C4A.jpg

http://www.uploadgeek.com/thumb-1478_4A8C3C4A.jpg

Any suggestions for improvement are eagerly awaited. In particular, ideas of how to make low-poly trees/bushes that would look good at that scale would be great.