There was a halloween weekend.. Why not do a Christmas month? The xp multiplier doesn't have to be ON from the very start, mybe from xmas to newyear will be enough. But the xmas themed goodies, treasures, guns, skins, taunts etc should be there from the very start of the december all the way to first week of January. That would be great ND.
Please ND, make accessory sets (look or theme of the acc matches from head to toe, no bonus stats) instead of just 1 item and have no other item to pair it with. Unique hats works great with TF2 but i think this would be better.