If you've been around Warcraft a while, you might recognize it. The icon itself is basically WoW's default icon-- whenever there's a spell or an item that doesn't have an icon associated with it, that guy's face gets put in its place. Usually, it's the icon for spells that players never actually cast themselves, such as quest spells or special item abilities. In this case, it's likely that Kael's client software harmlessly glitched and showed the wrong icon.
But who's face is it, exactly? That icon is actually a man who's created a lot of iconic artwork himself-- it's Samwise Didier, Blizzard's longtime art director. He's tons and tons of artwork for Warcraft throughout the years-- a look at his art gallery reveals lots of amazing work from all over Azeroth. He's even done a little voicework, in both WoW and WCIII. He has a thing for pandas-- he actually created the Pandaren-- and there's lots of "SD" and "Sam" in-jokes throughout the games he's worked on.
Oh, and he's also the frontman of Level 60 Elite Tauren Chieftain, the band of Blizzard employees that played at Blizzcon (that explains Drysc's mysterious "L60ETC rocks!" comment in the thread Kael posted). Basically, he's a WoW icon in every sense of the word.