How about another smaller cake with gumpaste or live flowers on top of it?
Floral arrangement or a picture of the young lady 8x12 in a fancy picture frame with flowers around the base of the picture.
A 3 or 4 tier dessert stand with mini cupcakes or cookies or even favor-size bags of candies.
To go with any of the great ideas above...you could also put small, clear lights (like Christmas lights) under the tablecloth, if you are using a white or pastel cloth. A friend of mine did it on her wedding cake table. Very Elegant!