I have good familiarity with Google Sketchup and would love to help out, but I don't know how much worth my contribution might be. But making little 3d models of ordinary villages, cities, farmland and such is something I experimented a lot with when I was distracted by the "worldbuilding" phase of my novel-writing instead of the actual writing. (I eventually gave up the concept and moved to straight 2-dimensional art for my map.)
Looking at Mighty Empires, it'd be pretty easy to make some low-poly representations similar to those villages and towns. I imagine you'd want a number of variations on basic forms. Would you want these to represent the cities and towns from the cities and townsland regions, or would you want to scatter little "villages" all over the place (since they would be in reality) as well?
Now that sounds really promising. Yes, please!
I can help out with textures if you need them, I own a copy of
FilterForge.
My main concern are towns/cities and strongholds. For starters, a single stronghold model and two or three city models (a town, a small city, a large city) would be sufficient.
For the villages, they're optional. We're on a world-map level, so realistically they wouldn't even be visible. I'm thinking about representing rural regions with the typical fields scattered around rather than village models.
