I have seen ornaments used as favors and seating cards.
Snowflakes as decorations too. Both on the cake and spread around the room.
If you are having a reception you can play the instrumental versions of some x-mas songs.
If you like having greenery around the room, consider a few pine trees with white lights and just a hint of decoration. Maybe snowflakes, ribbons, or a few glass balls in your colors.
You could sprinkle fake snow on the tables.