Well, I mean, how should the server be layed out? Freebuild? Blockparty (Same as Badspot's but a different theme)?
I'd feel a blockparty would be the best idea.
A freebuild will attract a lot of spam.
Also if it's not just going to be about build I have some ideas.
A DM on a giant Christmas tree would be good, also a KOTH or Capture point at the top in the form of a star would be neat.
You could also do an Elf vs Snowman TDM, or just a plan ol' snowball fight Fortwars server.