Blizzard provided Blizzplanet and other fansites a piece of artwork by artist Brom. It's not a piece of art created to be an official Diablo III concept art. It's an artistic interpretation of the Archangel of Justice by Brom. His personal artwork. Feel free to create a custom wallpaper, avatar or forum signature.
You will see this new artwork soon at the Diablo III Facebook. Thanks to Blizzard Entertainment and Bashiok (Community Manager). We will likely see more content or previews as BlizzCon approaches.
Note: Hold down the right-button and choose "Open image in New Tab" for the high resolution. (1280 x 1621)