I really like a lot of these suggestions. I have played a number of things at weddings that may or may not be more unique. I also really like the mention of Liszt's Cantique d'amour - what a beautiful and underplayed piece. Obviously the Benediction de dieu dans la solitude is an absolutely stunning piece from this collection, but it is very long and might not be what you want (unless this is while people are sitting down and so forth, then you could easily fill time with this). Otherwise, maybe paraphrase from this piece (such as playing the first third of the piece before the choral section). I have some other suggestions listed below. Good luck in choosing and hope you play well and have fun.
1. Chopin etude Op.10 No.3 (I usually play the beginning of the piece, before the middle and more difficult section, and the repeat of this section at the end. Just beautiful. If it is a more musically accepting crowd, could maybe play the entire piece).
2. Liszt sposalizio from the second year of pilgrimage (this is literally translated to marriage)
3. Liszt les cloches de Geneve from the first year of pilgrimage
4. Rachmaninoff prelude Op.23 No.4
5. Chopin etude Op.25 No.1
6. Liszt Au lac de Wallenstadt from the first year of pilgrimage
7. Liszt Au bord d'une source from the first year of pilgrimage (I think I'm seeing a pattern...)
8. Liszt/Schubert ave Maria (S558 No.12)
9. Liszt consolation No.3
10. Scriabin poeme Op.32 No.1
11. Rachmaninoff variation 18 from the rhapsody on a theme of Paganini (arranged for solo piano)
12. Scriabin prelude Op.16 No.1
13. Scriabin prelude Op.16 No.3
14. Scriabin prelude Op.17 No.3
15. Scriabin etude Op.8 No.8
There are just too many to suggest. I think a number of works by Debussy, Liszt, Chopin, and Bach would work really well. Have fun picking.
-KC