Personally, my main inspirations for the game are fairy tales and Disney movies. The sort of standard that I generally use for determining if something can fit in the game - if it's not too dark, or too cheesy, or whatever - is "would this happen in a Disney movie?" I think we've stayed within those boundaries pretty well, heh.
As for the music, I can't speak as to the composers themselves, but the references that I gave them were mostly film or game music, ranging from Nightwish to the Golden Sun Soundtrack to other visual novel soundtracks.