We don't know where this is from, and the picture is presented by Blizzard with the comment, "Interesting." So we know it's a glimpse at something coming up. What could that be? It's possibly related to patch 4.3 or the next expansion. And on that note, it wouldn't be outside the realm of possibilities for Blizzard to start dropping hints for the next expansion now.
Our staff picked up that it's a generic Stormwind building right away. In fact, the NPC and layout looks very similar to Cordell's Enchanting in the Mages District in Stormwind; that's pictured below. Obviously, the doodads and room decorations are different, but the layout and NPC spacing are the same.