You know, Ivern is perfect for a Christmas skin.
Saint Ivern.
His passive would put a white-blue design around the camps, and would look like snowflakes. Make it snow when you release them.
Q is a blob of snow, and you get partially buried when he hits you and roots you.
W could be snow-covered grass with Christmas lights on it.
E could be a snowglobe, and explodes in snowflakes when it times out. (Maybe have a few notes of something Christmas-sounding as it's active?)
Daisy could either wear a Santa outfit on her base look, or could be a walking Christmas tree complete with decorations and whatnot.
Then Ivern would be wearing a Santa outfit, complete with a bushy beard. His backing animation would be him going through a big bag (Santa's bag) and pulling out a present. ^^