That's actually what I was wondering if was available.  I started working on a "random rock" per se...a primitive sphere with a texture, and a displacement map of a large pattern granite plugged into displacement, and displaced pretty significantly.  I hoped I could randomize (via some node) the granite pattern such that every time I clicked the prop to add a new one from the library...it gave me a different shape.  Didn't get that far....yet.