Cool! I love such unique things. Of course, I don't use much postage -- except at Christmas -- but, I do like them.
One of my FAVORITE stamps that USPO had was one with the heads of carisole horses, 1994. I still have about 15 of them.....32 cent ones. But, hate to use them because they are all I can get.
So, I may have to order a few of these with MY OWN minis on there. Of course, with it going to 39 cent soon, better get some with the correct postage