Glowing Eyes: Save finished toilet paper rolls, cut eyes into them. Put glow sticks in the toilet paper rolls. Place the rolls into your hedge, trees or bushes at night. Watch people freak out as they pass your lawn.
They're Watching From Below! - This spooky effect would be easy to create and it would be a great setup for a dimly lit area which is visible, but off-limits to party foot traffic.---The big trick for me would be not to trip over it pre-party.