I thought I'd try another Sketchup model from the warehouse, and this is a version with the Rathaus Nördlingen by digitalstonemason. As with most things Sketchup Warehouse, I'm unsure of its copyright status, but it's a model you can download and use (somehow?) it just isn't clear what the limitations are! I hope the author doesn't mind.
The issue that concerns me here is that sketchup models seem to look a bit "washed out" which could be that my buildings are too contrasty, or, the use of photographs in Sketchup tends to lead towards lower contrast. It's pretty though, even if it's probably the wrong way round !
However, these models do seem to convert across with all their image_maps and these can be altered.... if only we knew the usage limitations!!! Aaaargh.
Sorry, it's been a while since I fired up some aspects of this thing. 3dtg currently has 3 detail levels I can render it at (aside from the AA settings).
level 1 makes all my "vanila" buildigs yellow, with red roofs
level 2 uses pigments and "normals" with just the windows added as image_maps - the above image is level 2
level 3 uses all image maps (200x200 pix ones I mentioned earlito er) and this level crashes POVray on my Bendford testbench.
Chances are that a smaller town will run at level 3. It's the sheer quantity of buildings involved I think stuffs it.
It may be that using a different file format and decreasing colour depth might fix some of this. That may be why sketchup looks washed out? So many things to test.
You did ask about what buildings need to be done, well, that's a tricky one. There's any amount of "one-off" type buildings one could make - all of these I would categorize as "specials" like this Rathaus here. You don't want two of these. As such, pretty much anything goes that would fit into the fantasy/medieval style genre. Most buildings don't really identify what they are by their shape. Some do, obviously.
If and when I can get more Tutorials written for potential POV users, then more of the vanilla style randomized building macros can be created. One challenge I'd like to get my teeth into is the "corner building" - things that could work as Taverns and Inns and the like.
I only have 2 ships at the moment - a galley and a cog. No mages towers, courtyard buildings like monasteries or barracks and the like. I could go on.
One solution in sketchup (like I have done in POV) would be to make bits of buildings that can be randomly connected together, the trick is working out a good algorithm - and randomizing the colour schemes.. coooeee.
That newest image looks pretty close to what Lankhmar would be. The number of intersecting buildings on that map is overwhelming. Your program would probably do it justice.