I’ve sang a lot of different tunes at chupos. Some were my idea, others were requested by the chassan/kallah. Here are some of the things I’ve sang Mi Adir and Mi Bon Siach to:
Odcha Hashem Elokai (old tune, not sure from where)
Boei B’Shalom (by Avraham Fried, I believe on the All Star Cast album)
Od Yeshvu (MBD, The Double Album)
Mi Bon Siach (Lev V’nefesh 2)
Mi Adir (Aish)
Machnisei Rachamim
Here are some nice tunes I’ve heard for people walking down to the chuppah (that aren’t commonly used):
Hinei Anochi (Tzlil V’zemer 5)
Al Taster (Shmelke’s Niggunim, then an album called Mimamakim, then Abish Brodt on Machnisei Dimah)
I’ve also heard songs that people wrote themselves and then walked down to them.