Well.. if it was me and they said in the thread what colors they like for winter, I would let that be the driving force, but I would maybe pick an element of their sign up sheet colors to tie in to that. Like.. just as a for instance.. say they said they liked blues and whites for wintery colors, but their decor is reds and beiges. I would make a primarily blue and white and put like.. red "berries" or something.
But that's of course, me... haha.. do whatever you want :P