Some hacker cracked open NBA 2K13's files with a hex editor, found 17 uniforms on the disc that aren't yet exposed in the game, and created a roster file with all of the jerseys available. One is the notorious "THUDNER" alternate uniform for Oklahoma City, which will almost certainly require a patch to correct—if that can be fixed with a patch.
NBA 2K usually puts all the uniforms the league has approved into the game at release, then if any are new, waits until they are worn in real life to roll out a title update that unlocks them. They're not on-the-disc DLC in the sense that you have to pay for them. They're free. But the NBA, like the NHL, doesn't want its teams' uniform debuts to be trumped by a video game.
If the THUDNER misspelling is not patch-addressable, I'd expect 2K Sports to simply not unlock it after Oklahoma City wears its new alternate the first time. The other 16 uniforms on the disc all appear to be correct, although some of the Christmas Day getups are eye-watering in their lack of contrast.
The Bulls are wearing red-on-red threads and the Clippers' blue-outline-on-red togs are only marginally more distinguishable. The Heat, at least, outlined their lettering in white. The other teams have more sensible designs, probably the most festive being the Celtics, with traditional green base and red lettering. I think. I'm colorblind, you know.
Teams playing on Christmas Day have traditionally added holiday trimmings to their uniforms, usually in the form of patches or embroidery or players wearing special shoes. This year they will wear altogether different shirts and shorts.
So, scroll through this gallery to see the 10 Christmas Day uniforms to be worn by the NBA teams playing Dec. 25, per NBA 2K13. (You can click on the magnifying glass icon in the lower right corner to enlarge the images). There are also seven alternate uniforms not yet available in the game, but already revealed by their respective teams. Except for the Thudner, of course.
Chicago Bulls, Christmas.
Boston Celtics, Christmas.
L.A. Clippers, Christmas.
Denver Nuggets, Christmas.
Miami Heat, Christmas.
New York Knicks, Christmas.
L.A. Lakers, Christmas.
New Jersey Brooklyn Nets, Christmas.
Houston Rockets, Christmas.
Oklahoma City Thudner, Christmas.
Philadelphia 76ers, alternate uniform. (from 2011).
SPortland Trail Blazers, alternate uniform. (Already revealed)
Cleveland Cavaliers, alternate uniform. (new, already revealed)
L.A. Clippers, alternate uniform. (new, already revealed)
Denver Nuggets, alternate uniform (new, already revealed).
San Antonio Spurs, alternate uniform (new, already revealed).
SOklahoma City Thudner, alternate uniform. (new, not yet revealed)