There are a few things you can do to make your Christmas tree look full. First, try to use the same size ornaments all the way up the tree. This will create a more uniform and balanced look. Second, try to use different types of ornaments to add variety and texture. This can include shiny, glittery ornaments, matte ornaments, and even some that are covered in sequins. You can also use different sizes of ornaments to create an interesting visual effect. Finally, make sure to fluff the branches of your tree to create a fuller appearance.