Winterfication! Turn your world into perma-winter.

Grass and podzol become snowy regardless of biome. Coarse dirt appears as snow blocks. This is accomplished through changing the models to point to the appropriate textures, so this ought to work with any texture pack you're running. Trees appear as snowy - Again, a model change and the snow is an overlay to whatever else you've got going on.

Tall grass and Double Tall Grass appear as assorted wintery shrubs. Red flowers appear as holly berries. Rain has become a simplified version of vanilla textured snow.

In addition, the villagers appear as Santa (cleric) and his Elves (all the others).

I'm marking this "100%", but I'm open to suggestions on ways to make this even more wintery while still working with most texture packs.