I've used a cubemap approach to render procedurally generated asteroid geometry and it works pretty well. I start by generating the heightmap using 3D simplex noise, Then when rendering I use a domain shader to offset the vertices of an icosphere along the normal vector according the the height in the heightmap.
I've got a bunch of other procedural content generation blog entries over at http://www.junkship.net, including this entry http://www.junkship.net/News/2011/11/13/building-steam-with-... which covers a lot of similar ground to the parent article.