Help! Need slideshow song for sister's wedding. Looking for something fresh & alternative with unique vocals.

Need wedding songs! My sister and her fiance are a young couple who is into a wide range of music. I'm making a slideshow for them and I'd really like to find something OTHER than the theme song from Aladdin or "A Groovy Kind of Love" by Phil Collins. Both the bride and groom are into alternative music, but I still want to find a song that is meaningful enough to put to this slideshow. I want it to be an uncommon (not traditional) song with unique vocals, but also not something that is too loud and in-your-face. Something piano or acoustic, maybe. I just want it to sound pretty, original and cly, but not to the point where the crowd will be falling asleep during it because they've heard the song before a thousand times (a.k.a. Kelly Clarkson's "A Moment Like This"). I've been thinking for days and my brain is becoming numb, so any suggestions would be GREATLY appreciated! Thanks a lot!