Although I collected some good flat rocks to paint on, during our last trip, it's been a while since I actually got the paints out. Here are some of the things I did in AZ last winter
The one above is a chunk of palm tree and the one below is the center part of a palm frond.
The real charm in painting rocks is this: if you don't like it, you can always relocate back to the riverbank or seashore and walk away. Maybe someone will find it and be amazed or maybe not.