A few moments ago Blizzard posted the above image on twitter. There is no hint on where this mount is going to be available from, but since this is a reward we can be sure that it wont come from the Blizzard store.
As you may know this November World of Warcraft will celebrate it's 9th anniversary. Starting wit its 4th anniversary players who logged in into the game mid to late November were rewarded always with a Feat of Strength. Now, from time to time we ever saw rewards like pets and experience gain buffs.
Our guess it's that this colorful mount is going to be the reward for WoW 9th anniversary.
What do you think? Do you believe this mount will come from other sources? Maybe something related to BlizzCon?