Cha--ching! The cash register rolls over once again.
Since we're talking about teenagers, I don't know if you can get your DD's picture on a bottle of soda. Most of the weddings that I've gone to that have had favors had a bottle of wine with the bride and groom's picture or names and date on them. The only other favors I've been given that were very nice was a lovely letter opener, a very nice pie server, and silver plated salad forks. Somehow, I just don't see kids liking any of these things, though.
Can't your cousin come up with a list from which you can pick?