I've been cruising around Pinterest a bit lately and stumbled across some cool boards with lots of photos and information on different types of artificial rocks. Most are for residential applications like covering septic tanks and hiding water well risers, backflow units, utility boxes, pumps etc.
Lots of good photos. Address rocks to!
Here's a Pinterest board on artificial rocks.
And here's a board for a company called RocksFast that specializes in fake rocks and other related stuff.