Fresh Flowers
Fresh Flowers artfully arranged in an oasis that has been soaked in water and placed inside of a plastic container. Affix the oasis with floral tape first and then affix the container to a small circular piece of glass or mirror.
For variations of this tip, use any container you choose such as a small wooden birdcage painted white or a little white basket. Do not use anything heavy as it could sink into the cake or tip the cake.

Silk Flowers
Using a thin coat of clear glue or silicone, affix the bottom of a wine glass to a circular mirror or clear glass. Fill the glass with silk flowers and tulle, fake glittery snow (if the theme is winter) or any other lightweight material you choose to keep the flowers in place without adding heaviness to the top of the cake. Finish the bottom by adding more tulle or glued flowers or both at the base of the glass.

Framed Photo
Purchase an elegant ceramic or crystal frame. Choose a size that will enhance your cake without overpowering it. 5″ x 7″ should be a good size. Insert a favorite picture of the happy couple. Place the frame on a thin piece of Styrofoam cut to fit the top of your cake. Using poster putty or glue (hot glue will melt the Styrofoam) affix the frame to the Styrofoam. Cover the Styrofoam in silk flowers and puffs of white tulle. Drape a strand of white pearls over one corner of the frame and let it flow along the flowers below.

Sheer or Opaque Wired Ribbon Bows
Using wired ribbon of your choice, in the colors of your wedding or in shades of opalescent white, place one 3″ bow on the top tier facing up. Allow the tails of the bow to hang down a few inches. Next, place five 2″ bows on the tier below, evenly spaced around the cake. Repeat for each tier.

Candles
Glue the bottom of a martini glass onto a small circular mirror or clear glass and decorate with tulle and small white flowers along the base of the glass. Place a floating flower-shaped candle the martini glass (filled with cold water.) Light the candle just before guests arrive.

These ideas are meant to give you some helpful hints. Feel free to follow them step-by-step, or just take bits and pieces of them to come up with your own special twist.
Happy creating and best wishes for a long and happy marriage!