There is an ancient New Year's custom in parts of Wales that has been resurrected (!) a bit recently, after suffering a strong decline in the mid 1900s. The Mari Lwyd (also spelled Fari Lwyd, but still pronounced mah-ree loo-ed or mah-ree loyd) is a mask representing a dead horse come to life - after all, the dark winter in Northern countries is full of festivals that use symbols of new life and light, from Yule logs to Christmas trees.
The Mari Lwyd is a rather spooky creature - the skull of a horse is mounted on a pole, then draped in a white cloth which hides the person carrying the pole. Ribbons and bells adorn the mask, and the festive troupe carrying it goes door to door singing songs. Sometimes the mask is made so that the jaws can be moved, and the Mari Lwyd snaps at people passing by. Traditionally the songs culminated in an exchange of insults in rhyming form at each door; today it is more common for the group to sing Christmas carols.
Here are some more resources for learning more about this interesting pagan tradition:
This Welsh folklore website has detailed info and a good picture, as well as info on related customs.
The National Museum of Wales has a couple of very old photos and some good text, too.
I also enjoyed some of the photos on flickr - take a browse.