I'm talking ice skins, cold camo, cold outfits (fluffy hoods), frostbite, ice grenades (skin), sliding down slippery slopes, falling on your ass and rolling down a hill, ice breaking if too many players get on it, ice breaking if there's too much weight, being able to kill people by shooting the ice out from under them, etc.
Thermal vision would be a cool addition too. Could be more effective when it's cold.