Get a local jewelry store to donate a nice necklace and earrings. Display it surrounded by 100 small, beautifully-decorated boxes. Guests purchase a box for a chance at winning the jewelry. Have the “unveiling” later in the auction, so other guests will see the boxes sitting on the dinner tables and be inspired to buy one too. Have some kind of a theme-related memento for the “loser” boxes and a special memento for the “winner” box. If there are unsold boxes, you can auction them off as a group to the highest bidder.
Sponsorship tip: include a coupon or discount to the jewelry store in the losing boxes.
Another variation of the Jewelry Box Game, this one involves prizes of all kinds. Have a stack of 100 red satin boxes (or gold or purple, etc.) at the registration table that people can purchase for $100. Each box contains a ticket for a prize worth at least $100: flat screen TV, plane tickets, laptop, dog grooming, chainsaw, skis, etc. At the end of the evening, guests get to open their boxes and claim their prizes. Again, unsold boxes can be auctioned off to the highest bidder.