This topic is meant to be an public prefab collection of the most useful prefabs.
Prefabs are used (as far as I know) by Soldat Polyworks and are basically small set of polygons that can be exported and imported. This is good for sharing useful pieces for a map, such as a well-built building, a well-shaded rock, good bridges, etc. I don't know exactly what properties you can export, but I know that it can export multiple polygons, their shading (colors) and textures.
I hope this will be useful for map-amateurs so that they can use pre-made polygons and incorporate them in their maps.
Share please (as attachment). I'll put the good ones up here.