Pie! Copa, you're making me hungry - and we just finished dinner!
I like the Ugly Sweater idea; Miss KT and her friends go out to dinner for their Ugly Sweater party every year.
You definitely need some kind of a theme. Hubby and I went to a Winter Wonderland open house one year. The hostess went with an "after ice skating/riding in an open sleigh" format, with hot cider, gingerbread cookies, and various finger foods, both hot and cold.
Speaking as someone who is not terribly graceful - please make sure the snacks are easy to eat while you're standing up talking to people! I have an awful time balancing plate and cup with foods that require both hands to eat, and I hate to put something down and possibly ruin a table or spill on the rug.