This is something I did for a friend a couple of years back..
I bought a picnic basket, some pretty tins, a candle (adding a book of matches), champagne flutes, cloth napkins, two small pretty plates that I found at a garage sale, and a couple of forks. I put in a bottle of champagne and took the basket to the reception. The caterer packed the tins with sandwiches and wedding cake and gave it to the couple to take on the honeymoon. It was a big hit.
You could make a small picnic groundcover/tablecloth and napkins yourself.. even line a basket to match.. If you know the brides wedding colors, you could coordinate.