I know that if I wasn't having fun painting rocks that I just wouldn't do it. Right from the beginning, it's been a creative challenge each time I get out the acrylics and brushes.Aside from the standard glow-in-the-dark feature, I've been devoting some more time adding a dimensionality to the rock.
Online I found this black paint by Stuart Semple which supposedly is the blackest black. He claims that his most recent iteration (black 4.0) is hands down better than any out there. It's a flat black, that obliterates, or more accurately...disappears objects painted with the same paint, placed in front or behind.
After ordering some, I've tried it on a couple of rocks and was amazed at the results. The bowls or basket rocks as I call them, have an oval black center that is offset slightly thereby giving an illusion of depth. I placed a comical figure with their nose and fingers hanging over the edge to add to this sense of depth perception. Kilroy ( the martian, in this case ) lives on.
I've used the same technique on smaller rocks with some success, always remembering to use brighter colors to enhance the foreground and the very dark black to draw one's eye in.
Although you can't experience it here, I have a pair of 3-D glasses that really make things jump. Stop by my table at the farmer's market to check them out.