Not sure how far you are with the rock so you might have thought of this already, but t would be good to get some deeper cracks into the rock. for example:
Depending on the engine you're using and how flexible it is, you could try using your AO as a mask, like this: (the in-game example is rather crud, this image is oldddd)
Whoa, what's with the criticism. I thought the op is advertising his 3D printing service and showing off an example from an artist who bought and paid for the service.