It's hard to recommend something for someone you don't know.
However, perhaps as part of a present, you could do up a photobook of pictures from the wedding (you could use photobox.ie - I've used them and they are good) as I'm sure the couple will be dying to see photos.
Unusual presents that I've heard people say were their favourite wedding gifts include:
- a photo from the turn of the century of both spouses' home towns (got from the Historial Picture Company, I suspect) framed together;
- a courting seat (maybe if they have a garden a loveseat would be appropriate either)
- two hurleys (the couple were living abroad and now fascinate their neighbours when they go out for a puc about!).