I received it on a postcard from Germany. (Love the snowdrop.) If you go to this website and can read the German you too can order specialized postage for your postcards or letters.
In the USA you can do this too - if you are willing to pay more than the marked rate on the stamp. The US Postal Service offers zazzle stamps, at US $19.99 to $20.95 for 20 stamps. Here are two of my favorites.
You can also make your own specialized postage, using your own images, at zazzle.com. It looks pretty straightforward, and I might do it someday. I hope Dorin will add some more information, as he has produced these special stamps and shown them on his blog.
A question: will some of these become very collectible? They are limited editions. Will stamp collectors snap them up?
Theme for next week: Children's artwork on stamps, or stamps that would appeal to children (cartoons!)