When an admin features my image in a group, the first thing I do is tweet the group. I find these tweets see more interaction and any others I send.
I think part of our sales comes from how several members / admins tell me that when a new image is added to the group that google finds them. They also say, when your in a group, featured or not (though it helps to be seen on the front page), your image is then associated with others. and without having to add new keywords, or spam words, people can find your image through random google searches and your image will show up in the group or contest. Never underestimate the power of groups here.