I decorate my trees every Halloween with plastic pumpkins. $20 worth of plastic pumpkins and a drill gives you a lot of bang for your buck.
Head out to Walmart and pick up 10 to 20 $1 pumpkins. Drill a hole in the bottom so any rain water drains out. Tie to tree limbs and BAM you have your own Halloween tree. Halloween night I put glow Sticks in them for an eerie effect.
Cheap and simple yet still Pinteresting.