It seems you are looking for something original and quite different...

I was thinking maybe something like this..

I know you love to take pictures .. Why not do a photo book of all the times you have from the time they started dating to the time they got married .. The photo album could be personalized with a little story of how you saw them from the time they met onwards.. and all the important times they spent with you and others.. Collect the pics from all you know that have pics of their courtship sort of like a living story with captions under each pic ... The last pics should be a large one of them on their wedding day...

Something else a poem or a song made just for them... written just for them... and composed for them ..

Then have the words put on a nice background and frame it.. With a brass or gold plate at the bottom with there wedding date on it...

A bit off what most are suggesting .. but different indeed.

just my thoughts rapid as they are lol

hugs
snow