Christmas trees and stars are definitely the best ideas for Christmas origamis. These are the most common. It's easy to make them peppy and exciting by using different Christmas colors and designs. I've even seen someone make an origami Christmas wreath by basically attaching many Origami stars in a circular shape. It was so creative and so cute.
Another great idea is origami Christmas gift boxes for Christmas treats like small cookies and candy. This is what I'm planning to do this year as favors and also as stocking stuffers. It will be fun.