And I would say it isn't necessary to try to make it any particular style or theme. In fact, there are a LOT of possibilities if you look at all the observances that take place during December and January. For instance, limiting ourselves to musical remembrances, we have:
Dec 9-Techno Day
Dec 11-Choral Day
Dec 13-Violin Day
Dec 29-Cello Day
If you like animals, we have:
Dec 4-Wildlife Conservation Day
Dec 14-Monkey Day
Dec 15-Cat Herder's Day
Dec 16-Underdog Day
Jan 1-Polar Bear Plunge Day
Jan 2-Happy Mew Year for Cats Day
Jan 14-Dress Up Your Pet Day
Jan 16-Appreciate a Dragon Day
Jan 18-Winnie the Pooh Day
Jan 20-Penguin Awareness Day
Jan 21-Squirrel Appreciation Day
Jan 22-Answer Your Cat's Questions Day
Then there are days having to do with food:
Dec 1-Eat a Red Apple Day
Dec 2-Fritters Day
Dec 8-Brownie Day (unless this means scouts or little elves)
Dec 10-Gingerbread Decorating Day
Dec 17-Maple Syrup Day
Dec 25-Pumpkin Pie Day
Dec 26-Candy Cane Day
Dec 30-Bacon Day
And the whole month of January is "Hot Tea Month"
There are scads more of these. Just do an internet search for something like "daily observances" or "international special days" and you'll get a variety of lists. They aren't all the same, but you're bound to find something that works for you if you don't feel like doing something more traditional like Christmas, Hanukkah, or Kwanzaa. There are other religious observances, as well.
And, like Paul said, make it family friendly.
Vicki