The bride and groom may decide to stay at a hotel or in their own home on their wedding night, either way as a member of the bridal party - or a thoughtful friend - you may want to have a special gift waiting for them when they arrive or delivered soon after.
If they are staying at a hotel you can talk to the concierge about having champagne, chocolates or strawberries delivered to their room after their arrival or waiting when they arrive.
For couples spending their wedding night at home try and get a key to their house or apartment and set up a romantic setting in their bedroom with food, drinks and maybe flower petals scattered around the room. Stay away from candles since you don't want to light them in advance and unlit candles aren't as romantic.
You can also call the hotel the newlyweds are staying at on their honeymoon and surprise them with room service, dinner at the hotel, spa treatments or champagne. I always find that when you tell a hotel that the couple is on their honeymoon they go above and beyond to make their stay memorable.