Add a fun item to gift certificates that are up for bid to draw more attention and enhance your display.

If auctioning off a gift certifcate for a round of golf, place the certificate in a basket of golf balls...

...If auctioning off a camping trip, add s'more makings (graham crackers, marshmellows & chocolate) to your display. Add a scented candle or lotion to a gift certificate for a massage. Any creative display will help attract attention to your item and make the purchase that much more attractive.