As we reported, Blizzard recently created a mini-site in honor of the fifth anniversary of World of Warcraft and the 15th anniversary of the Warcraft franchise. While the interviews and BlizzCast sections haven't been updated yet, the first piece of the Battlecry Mosaic has been revealed due to the photograph submissions of WoW players.
In addition, an early piece of concept art for the Dark Portal in Outland has been added to the site. Zarhym also announced on the official forums that Blizzard "will unlock the original full art piece of the faction leaders seen in the background of that page" when the mosaic is revealed, so keep submitting your photos!
We'd also like to mention that the Battlecry Mosaic page was actually designed and built originally by Wowhead's Skosiris during an internship with Blizzard's web team. There's another reason to send in your picture!