Ulu Watu, Freaks, Piranas, Skeelz, Berzerk, and Frozn. Those clans already have Noels of there own, that could eliminate them for this years Noel. And for the last two clans I've listed, were listed in the same year the respective clans were released. My best bet that the Huracan could be next in that chain (best bet being El Kactus).
You can check the image here: http://static.beta.urban-rivals.com/img/special/christmas-2013/background-day-1.jpg
1: All-Stars Logo
2: Frozn Logo
3: Looks like Hawkins Noel bag, Pirañas
5: Skeelz bag.
6: Olga's milk can, Freaks Symbol
7: Noel hat, has a symbol in it i cant figure out
8: Junkz logo
9: Lola Noel's boot (first level), Berzerk
10: Sakrohm's symbol
11: Lucas' hat, Bangers Symbol
12: Pussycats' logo
14: Dr. Saw's glove, GHEIST
15: Ingriss' case, GHEIST
16: Lola Noel's other boot, Berzerk
17: Montana hat
19: Looks like it could be the Vortex reference
20: Piraña bandana
21: Huracan mask
23: La Junta symbol
24: Montana symbol
25: Ice Block, Frozn
Missing references: Ulu Watu, Jungo, Fang Pi Clang, Nightmare, Rescue, Roots, Uppers, Vortex
@Mr midwife: Sue would make an adorable noel card. While Angelo Noel would be bratty as hell.
A Burdock Noel could be funny where his flower cannon shoot poinsettias, mistletoe, Holly and gifts. While it probably wouldn't happen, I'd like the Noel to be given to an old school card from the Apeka and Team Chaman days just so they can get some new life.