The most logical choice is white, but if you really want to showcase your winter tablescape, opt for a solid colored tablecloth.
Carolers: If you have a Christmas village collection, use it for a great tablescape complete with carolers, a sleigh and maybe a few snow creatures.
Do something unexpected - Just because your table is round doesn't mean your tablescape has to be predictable.
Scaling up your design to fit a big table is easier and often more rewarding that trying to make a tablescape to suit a petite space.
Grapes are good for wine themed weddings, and cranberries provide a bright punch of color on a dark tablescape.