Basically, make a group icon.
You guys vote on the sets.
I don't think Polyvore lets you vote for your own sets, but just in case; don't.
Honour system, kiddos.
12 winners. Just because it feels awesome to get that little notification "Congratulations, your set "_______" won the contest in this group!"
But the 1st place winner will be placed as the icon.
Enter as many sets as you'd like.
Make it beauty related.
And, uh, that's about it.
Good luck, you have until 5/22/10.