Barnstars are awarded to people for outstanding services to the community. The concept is described in detail on Wikipedia where it is also used extensively. There are no plans to do the same complex thingy in the OSGeo Wiki but whoever feels entitled to set up a template and upload the images please feel free to go ahead.
Initially I wanted to design a cool OSGeo compass barnstar but never got around to doing it. Instead of denying due respect to awardees by virtue of my own graphical incompetence I simply copied this one over from Wikipedia. Whoever feels like designing our own set of Barnstars, feel free to replace the image.