It has a hint of a Christmas theme, but it's not a Christmas story; Santa's in it, but he doesn't become a jolly gift-flinger until the very end. So feel free to include some holiday elements, but keep them minimal. Santa wears a suit of armor and carries a massive hammer at one point.
The main character is the Winter Witch. She wears a lot of black and a pointy hat, so everyone will know she's a witch. Her familiar is a red crow. She flies on a broom and just wants to be left alone.
It all takes place in the North Pole. Some primary locations are the witch's cottage, Santa's Village, and a massive castle with impossibly tall towers. Then there's Asgard, in the branches of Yggdrasil the world tree (though not much happens there).
It's a very silly story that relies on a large number of characters (Vikings, elves, frost giants, a druid who's turned into a tree, a necromancer who looks like Rasputin), so I'm envisioning a design that is very busy and features a lot of elements. Feel free to challenge me on that; it's not strictly necessary.