Why not replace the standard rectangular postcard pretty rooms? While this does not necessarily make it out of the paper. You can take the cardboard or even felt.
To create the cards use the proposed template (or draw a mitten).
Mitten better cut in two copies. In the case of felt-sew between themselves, in the case of paper and cardboard are glued. In a corner, you can make a hole to card was easy to hang on the Christmas tree.
The finished postcard decorate with ribbons, buttons and other decorations.