Have you ever actually played the game of marbles? I'm not sure I ever learned the rules, but I'm still drawn to the weight and colors of marbles and like to use those pretty glass orbs as paintbrushes instead!
Marbles grab the paint and make trails behind, leaving the most interesting designs. Mesmerizing to watch.
Just gather together a pan (cookie sheet, brownie pan, pie plate), some Clementine natural paint, heavyweight paper and a bowl of marbles.