I'll pledge $3 USD for every time Snape, Harry or Draco crossdresses or dresses up in "holiday" garb (keeping with the theme - this can be a santa suit, elf costume, solstice winter king, etc..) Note - while I prefer these pairings, it won't matter who Snape is paired with for it to count - so if it's Snape/Hermione, Snape could dress up or they could catch either Harry or Draco dressed up. For instance - they are sitting cozily by a fire when Santa Harry stops by to drop off presents.
If Snape shows up once in the fest dressed as a traditional St. Nicholas (not the red suit, the one with victorian velvets and all that fluff) - I'll throw in an extra $10. I'll do the same if Draco gets dressed as the Snow Queen or Harry's stag becomes a reindeer with a red nose.
I've supported Soles 4 Souls before so this is a fun way for me to do my contribution to them this year! *grins*