A GeekBadge costs 50 GeekGold.
A GeekBadge, along with avatars, Microbadges, Patron's Badge, and UberGeekBadges are used to customize your Graphical User Representation on the BoardGameGeek.
A GeekBadge can be thought of as an extra Avatar. It is located above the Avatar and is 80 pixels wide and 15 pixels deep. Note that the Avatar is 64 pixels wide, so there is some overhang. The content of the GeekBadge can be changed by the user at any time. The content of the GeekBadge is limited to color, border, and text that overlays the badge area.
Several Geeks use their GeekBadges as Avatar extensions. For example, the Avatar depicts a game and the GeekBadge holds the text "BGG IS GREAT".
GeekBadges can be upgraded to UberGeekBadges for 50 GG.
There is a GeekBadge randomizer by Bail Organa available here.