I borrowed this image from David's mail art site, Mail Art Salon. The entire composition is a gloriously colorful universe created by the artist. I couldn't find the exact painting this postcard was derived from but, I'm certain it must have been rather similar to this one shown here.
The other side reveals a curious display of postage placement as well as David's "Certified #1308" rubber stamping, declaring it an original. You can check out his interesting technique and his Mail Art call at his Mail Art site. Thanks for the card David and see you in the mail soon!