There's a software link in this forum category that points to a Random RPG City Generator - now this app only creates "line art" cities and towns, rectangles for buildings, gates and wall towers, lines for roads, city walls, blue for rivers, green for parks.

I wonder, if there's a way to use the random map generator code - which is rather intuitive, with user pre-sets and modifiers to tweak the output, (though the result is not what you're looking for,) altered to create 3D sprites instead of blocks and lines.

I'm not saying hack the program, but perhaps contact the developer and see what could be done to "frankenstein" the code so it works within GeoTerrSys.

It might be a rather awesome way to generate customizeable cities within your system - worth a thought, anyway...