I've painted on some of the strangest vehicles lately. A while back I agreed to donate some time working on a collaboration piece for a fundraiser. I ended up having to paint two areas on a life preserver. It was a little weird at first, and definitely challenging to work the acrylic paint into the texture of the float, but it was nice to paint on something unconventional. I decided to go with an octopus, and some fishies with an anchor.
I'll give you a hint. Undergarment.