Make it snow on the Rift!
http://i.imgur.com/2UCbeC7.jpg"
If nothing else, I'd love to see a snowy Summoner's Rift this year for Snowdown Showdown. It doesn't need to be as harsh as the Snowdown map of old, but a little bit can go a long way: ice-tipped trees, falling snow and snowflake particles, and blowing wind SFX would make for an awesome atmosphere in my opinion! The hue of the map could also be tuned slightly to make it look whiter/chillier.
Might be a bit too late for this suggestion, but it's worth a shot :)