http://www.eventhubs.com/news/2011/sep/21/character-themes-new-fighters-ultimate-marvel-vs-capcom-3/Character themes for the newcomers (sans Nova, RR, Phoenix, and Frank).
For the Capcom cast, they are all remixes of themes from their respective games.
Nemesis: "Unstoppable Nemesis" (a boss fight late in RE3, after the clocktower events).
Vergil: "Vs. Vergil 2" (second battle with Vergil in DMC3).
Strider: His MvC1 theme remixed, which I believe is a remix of the intro to his game.
Firebrand: The main Ghosts n' Goblins theme, re-remixed for him (I think).
