FOSS gamedev and creative worlds

I have been looking over the existing code and am wondering if there is some sort of facility for making items that are not standard cubes/flat sprites. Has this been implemented yet? If it needs implementing, what would be the preferred approach. I'm thinking of a sub cube voxel based solution.

Irrlicht support MD2 models AFAIK, see the thread about 3D meshes for mobs.