How interesting, I found rock painting by accident, when ask by a sister-in-law to paint her a lighthouse on one, I have mostly painted on old sawblades, any size an shape, once painted, the circular ones , I add a clock works to the hole in the middle, and hands, depending on the picture, sometimes,just the 12,3,6,&9. some no numbers as the teeth on the sawblades are just in the right spot for all the numbers, I just add a small dot, others I put on all the numbers.
Painted a welcom sign to hang on the front of our 5th wheel, an have been ask to paint one for others, I use there theam, or faviorite thing overlay with there name, theese are painted on a pice of plywood with severl coats of polyurthane so weatherproof . Some I give away some, some I sell. Mostly just have fun, hobby.