For starters, there's the introduction of the Sunwalkers, the Tauren Paladins and Priests, coming with Cataclysm. We've been getting progressive story bits about many of the new class and race combos as the patches progress, so it seems very possible that we could see Aponi and Tahu begin their training, with these new skins being tribal warpaint, a sign of their devotion to the sun. Could the wings be the Sunwalker version of Avenging Wrath?
The other possibility (which is strongly suggested by the black fur of the Taurens in the data mined picture) is that these could be Grimtotems. Rumors strongly state that Garrosh is killing Cairne in Cataclysm (or perhaps even sooner, especially since Baine looks like he may be making an appearance in Patch 3.3). I'm not so sure it'll go down that simply, and I'm more leaning toward an assassination orchestrated by Magatha. Either way, I'm also liking the idea of the Grimtotem allying with Garrosh in a move to consolidate their power in the wake of the political upheaval among the Tauren and the Horde. If Garrosh makes his move in Patch 3.3 to consolidate his political power and show himself a reasonable candidate for Warchief, being backed by a cadre of Grimtotem Bersekers painted for war would make him appear all the more awe inspiring. It would also explain why, according to the recent lore revelations from the PC Gamer UK article, Garrosh is still allowing Tauren in the middle of Ogrimmar when he's evicted the other non-Orc races.
Of course, the third option is that this a test for a new character customization option in Cataclysm, namely, tattoos. RPers and more aesthetically minded players know that it seems like pulling teeth to get Blizzard to implement cosmetic non-progression oriented character customization (Seriously, just steal stuff from LoTRO, Blizzard! I won't tell if you don't!), so even the whiff of a possibility for new stuff is pretty exciting. Then again, we've seen tatooed NPCs before, such as in the Wolfcult of Grizzly Hills, so this could still just be an NPC thing.
There's probably more things it could be, or it could be a thing that just stays in the files and doesn't pop up until Cataclysm, but either way, I'm pretty excited about the possibilities. Stay tuned to WoW.com. If they show up anywhere exciting, I'll be here to fanboy out with you over it for sure.
[Thanks for the link, Max!]