Being a boy mom is so much fun, when else would I have a reason to paint tiny vehicles on rocks? Our boys and I have been painting the alphabet letters and pictures on rocks to learn the ABC's. I was encouraged by friends to paint cars on rocks for sandbox/outside toys so I have made a few of these sets available on Etsy if you would like to check them out! We love playing with them in the sandbox, and also they are just adorable hanging out in our garden to enjoy.
Each stone is sealed to be weatherproof and fit for the outdoors. However, no sealer will permanently protect the painted stones left outside. I recommend spraying your outside painted rocks with a Krylon acrylic sealer if the design begins to fade with lots of love, or if you notice any sign of wear and tear.