The colour scheme indeed seems too aggressive for many people’s tastes; I still like it better than the alternatives suggested so far. However, the look will change anyway once there is support for textures. These would e.g. replace the monotonous green with a grassy pattern.

As for disabling the rendering of ground-level features in favour of Mapnik, that isn’t quite what we are aiming for - OSM2World does not just model buildings, but also things like sidewalks and lanes on roads, and we would like to display these, too. I’m considering a building-only rendering as an overlay for standard Mapnik tiles as a future project, though, once the current rendering process runs smoothly on the planned new server.