My daughter is too young for this type of project, but I am thinking maybe next year. I think this would be terrific project for a preschooler.
Puzzle pieces would be perfect. A wine cork, an old key, a popsicle stick, a pinecone, an interesting tiny twig. The child could paint all the pieces made out of wood and cardboard. An adult could spray paint anything made out of metal or plastic.
It would be tons of fun to harness all that energy and get your child to clean out their toy-box a bit. Everyone could paint and then the adult could hot glue the found objects down on some foam core. Amazing.
Can you think of any other found objects that could be used?