When you say rock only, do you mean just rocks and no plants, or do you mean Iwagumi rock style tanks?
Have a look through the links section on the main page. You will find some sites very inspirational.
Funny you mention this as, just this weekend I have been set up a 200L tank that will not contain any plant.
I really like biotope tanks I have a Amazon biotope tank that contains very few plants, and lots of wood. But the 200L tank will be South East Asian, river setup with lots of large rock and fast following water, the main types of fish i will be keeping in it will be gobies, maybe some hillstream loaches and some Barbs.
I suppose technically my smallest tank is a rock only tank, it doesn't have any plants just algae(Cladophora aegagrophila) & cherry shrimps, pics can be seen in my journal - http://ukaps.org/forum/viewtopic.php?f=35&t=1389 or just look at my signature