I think it would be great to have a Mardi Gras theme for a sweet 16 party. You can order beads, masks etc from a place like www.orientaltradingcompany.com and pass those out to all their friends and at the end of the night the person with the most strands of beads gets a special mystery prize(to help cleanup afterwards). If a car is the present your giving him or her fill a pinata up with paper scraps and put the car keys in it. But just make sure the person hitting the pinata is the birthday person.