It doesn't get much more simple than this. Rocket Elf isn't what I consider a simple stamp, but when you only color the tree it makes for a quick and easy card. I added a little glitter to the 'swirlies' with a Spica pen, but they don't show up well in the photo. You could make a stack of these cards in an evening.
Have you made your cards yet? I would love to see them, just leave me a link. Hope you are having a great week!