I have seen a faux stone spray at JoAnns and think at the home improvement stores. There is one type of spray that styrofoam won't handle though. Kind of melts it. Not sure what one, used it back in my floral arrangeing days. Might be different with the coolers because they are a denser foam. I am going to attempt this, love the stone planter looks, hey, I got it, make stones. Use the spray foam, pile it up, let it cure and then spray paint it. Don't know how long it would last. Might try spraying foam over a old brick to give it some weight so they don't blow away. Gee thanks Mary O, got my creative juices flowing. Right after I finish the half dozen quilts working on in dungeon.