I made this prototype of a Christmas card tonight - exterior decorations are very simple, all the time's on the pop-up tree inside. I've found a better template since - if I'm not happy with that I'll make my own up. Then make rather a few of these... and some other designs perhaps.
Template came from here, note the illustrations don't match the template provided with the tutorial, it seems those nice tree shapes are cut using a rather expensive cutting machine and die set.
Anyhow, took a bit of working out some of the finer details but I just love this card. It's still a thrill opening it up and having a 3D Christmas tree right there :D