This could be a carousel of events all happening at once during the holiday season. Each classroom sets up its own decoration, and you walk around to visit each. You could do Fall Harvest, Haunted House, Polar Bear Express, and New Years' themed room. Each room can have snacks and activities to complement the entire experience.
Have Houses partner together to design the classroom, then let students vote on their favorite. The winning House can receive extra LiveSchool points. Or you can have individual classroom design the rooms, and let the House with the most points be the judge.