Users marked with a star are gallery stars and have contributed a lot to the site. In particular, they clearly care about tagging pictures with meaningful keywords, contributing to common galleries rather than making their own and they bother to make up good short names and fill in decent metadata.
As a reward, these people get to play with new gallery features first, and end up being responsible for nearly all the good ideas round here.
There are currently just 8 gallery stars out of 1759 users:
Thanks to all of you.