Hmm, let me try my hand at this. A pretty eclectic mix, but there you go.

Magnagora: Crossroads - Clapton's version. (If you know the supposed meaning, this choice might make sense)
Serenwilde: Dark Side of the Moon - Pink Floyd. The whole album.
Glomdoring: Beautifully Broken - Gov't Mule. Judging from all the ing on the forums about their state.
Celest: Godzilla - Blue Oyster Cult. In the lyrics, replace Godzilla with Kethuru, and Tokyo with Celest

The Avenger: Karma Police - Radiohead. Ok, it isn't an organization, but this one's so obvious.

Here's my post, first I'll put in the music that comes into my mind while playing the game

After Evoking the Avenger: The Dahaka Chase from Prince of Persia 2, Warriors Within

Celestia (When not being raided): Balamb Garden (Orchestral Version) from Final Fantasy 8 or Blooming in the Church from Final Fantasy 7 or Cloud's Theme from FF7

Celestia (During a raid): Trail of Blood from Final Fantasy 7

Shanthmark: Cosmo Canyon from Final Fantasy 7

Inside Paavik Mansion: The Nightmare's Beginning From Final Fantasy 7

Shallach: Chasing the Black-Caped Man from Final Fantasy 7

A Celestian (mostly a novice) entering Magnagora or entering Nil: Makou Reactor from Final Fantasy 7

Battle between the Dragon Turtles and the Seawolves: Fortress of the Condor from Final Fantasy 7

Ethereal: If you open your Heart from Final Fantasy 7

Stewartsville/Delport: Parochial Town from Final Fantasy 7

Inside the Chataeu in Delport: Don of the Slums from Final Fantasy 7

Estelbar: Farm boy from Final Fantasy 7

Southgard/Rockholm/Angkrag: Mining Town from Final Fantasy 7

Okay now for Civilizations:

Serenwilde: Forested Temple from Final Fantasy 7/The Hobbits from Lord of The Rings

Celest: Theme of Rohan from Lord of The Rings

Glomdoring: Off the Edge of Despair from Final Fantasy 7

Magnagora: Clint Eastwood from Gorillaz

Well that's all I can think off when it comes to themes and soundtracks, so much for being a Final Fantasy Fanatic

No, the theme song for the Chateau in Delport is obviously Roxanne.

I have revised my theme choices.
Glomdoring's new theme is "I'm afraid of Americans" by David Bowie and NIN.
Magnagora's new theme is "Freak on a leash" by Korn.
Celest's new theme is the Banana Boat song, and Catarin will now be proceeded by the Banana Boat baby wherever she goes until she steps down, then the new office-holder will have it.
Finally, Serenwilde's song is "Follow me" by Breaking Benjamin.

Guido gets the song "Second Class Citizen" by Area 7.
Terentia gets "Bitch." by Alannis Morisette
Kiarlea gets "Cold hard bitch." by Jet.
Iblis gets "Three evils (embodied in love and shadow)." by Coheed and Cambria.
Catarin gets "Fiction" by Orgy. (she has to try, I suppose).
Oh, oh, oh, and Narsrim gets "Cheer up Emo Kid" by Patent Pending. He just wants some love.
And, of course, supersnuggly Munsia gets "Here's your sign" by.. someone. Forget the artist name.

"This is Halloween" for Glomdoring.

Maybe for glomdoring, Don't Fear the Reaper, by Blue Oyster Cult?
(Yes, that is supposed to be somewhat sarcastic)

I just heard 'Southern Cross' by 403 today and the lyrics hit a nerve. It's a perfect fit for Celest.

Lyrics here. And yes, it's in English. (Engrish?)