AIWIY is all I can think of. A really great marriage song is Landlady, but that's for later on, not wedding.
IALW is a bit too painful for a wedding. There's solid sentiment in there but the promises are mostly empty. I guess that's true of AIWIY too, though, and both songs offer a promise of something that matters at the bottom of it all.
The best marriage (not wedding) songs are Landlady and DYFL.