Perhaps a book on Japanese origami (paper folding) would help. You should be able to easily find one at a major bookstore like Barnes & Nobles or Borders.

Maybe making a swan with your name on one wing and your fiance's name on the other. When they unfold it they find the time and location and so on. This could get a little difficult to mail, so this may be too impractical. But it is an idea to get you started.

But I think origami books would help greatly here.