New avatars have been added to the Battle.net launcher, including all 39 hero talent specializations in The War Within!
Seen by other friends in the Battle.net launcher chat window, these icons allow players to add a small touch of personalization, though they won't be seen in-game, where common game or battle.net icons are used to display player activity instead. To change your icon, simply open the Battle.net launcher and click on the existing avatar in the upper right hand corner to open the selection screen and look for a new one.
There are a lot of avatars available and unfortunately no search bar, so it helps to filter by icons from World of Warcraft first.