You can have your own photos printed on just about anything these days - mugs, cakes, beachballs... why not postage stamps?
Why not indeed! In fact you can buy customized stamps with your very own masterpiece. For example, check out these four different implementations available at the US Postal Service website. Just for fun, I plopped one of my favorite photos, Ginkgo Serenity, into the mini-application to see what it would look like - not bad!
You don't have to go through the USPS website - just Google with a phrase like US postage stamps your photo and you'll find lots of companies that are authorized to create customized real US postage for you. Make your own commemorative!