BodyArt by Cat is providing free body art -- Blizzard themed or otherwise -- at BlizzCon.
There are standard BlizzCon related stencils as pictured above, such as being branded with the Wrath of the Lich King logo as shown above.
The body art lasts 2 to 3 days and is dry instantly. How do I know? Because I got me a dragon.
The artist can even be creative and use some of her other art to try to make you into a NightElf.
Cat's website is ecparties.com, if you are interested in contracting her services for your event.