In a recent tip of the week post, Moodle twitter account published one useful tip which is asked by a lot of newbie moodlers.
How to add badges with participants’ profiles like on Moodle.org forums?
Solution: These are the group pictures/avatars and not the badges. When you create a group in your course, you can add a picture to represent that group. In places such as forums this picture is then displayed for each participant. If they are a member of several groups then several pictures will be displayed.