OK, what you basically have is a straight forward "do as i do" trick. You could develop it into a relationship between 2 different spectators. A very good example of such a trick would be Derren Brown's "Romantic Card Trick" see below
http://www.youtube.com/watch?v=DiDIXoIAkcg
Anything along these lines would, I think you will agree, blow your spectators' minds. Obviously, the secret can't be revealed on this site, but if you think about some basic ideas, you will figure it out.
Good luck.