I thought I'd post the challenges and the banner in case anyone wants to start painting before they have a chance to update the site.
1-7: Snowmen (traditional or unusual)
8-14: Winter Wildlife
15-21: Winter Activities
22-31: Artist's Choice To End The Year
The December banner (which inspired the first challenge) of snowmen made out of sand. It's snowing at the beach, which is hard to see in the small version, but will hopefully show up when the banner is live: