old-skool paper chains, popcorn chains (sprayed with clear coat to keep them "fresh")

repaint/recoat the balls (you can pick colour themes for this - different ones each year)

get the kids to go hunting in the bush (thanking the universe/god/goddess whoever you subscribe to) when they pick up branches, unusual leaves etc from the ground to make wreaths

we used to go to the local prison and pick up the pine cones from under the trees and then decorate them

get the kids to make decorations from things around the house (old dolls/toys etc)