Well, you can create skins in Sketchup (but very limited as I think) or you are able to create textures from photomatch ressources (from photos which you can use to build geometry). But unfortunately Sketchup saves the skins asnon-power-of-two textures. So this was'nt interesting for me.

I am supposed to rather use the geometry as "3D-blueprint" to rebuilt it with decent skinning in other apps or even in WED. This might sound as "doubled" work but its worth it.