these are some rocks I used to make the hipoly rock walls. Generally the process I use for making rock goes like this:
1) create basic lowpoly in 3dstudio max (some of the rocks here are made from just a box)
2) import this to mudbox and subdivide with smoothing turned off
3) champher edges using the flatten tool and smooth to suit
4) use the freeze tools to mark out cracks and flakes then use the regular brush to recess or extrude these areas
5) use a mask to texture the outside
