I think Peppermint would be a nice look. You know, candy canes and stuff like that.
Snow, of course~ And Christmas music playing on the map.
And if you want a snowman, I have one that I could put up for download, as well as some presents and a Christmas tree I'm working on. A Christmas map sounds so much fun~
Edit: Oh cool, there are present meshes! And the Santa is pretty awesome XD