Video game soundtracks often deliver - I'm particularly fond of the Guild Wars soundtrack. If you want epic fantasy-inspired rock, I can suggest looking into the symphonic metal movement: bands like Within Temptation, Delain, Sirenia, Serenity, Pythia. If you prefer something more chilled-out, there's some great creative commons instrumental music out there; I particularly recommend Zero Project for being Mage Knight-appropriate:
I didn't know what to do with my UberBadge, so I left it as a GeekBadge.
I prefer to listen to instrumental music while playing Mage Knight. If I listen to anything with vocals, there's a chance I'll start following the lyrics or singing along, which ends up slowing the game down - and this can be a long game. It could be just because I bought the album at the same time as I bought the game, but I find Mogwai's 'Hardcore Will Never Die, But You Will' to be a great soundtrack for Mage Knight. The two are inextricably linked in my mind.
I enjoy newer, somewhat dark, primarily electronic music with MK. For me, the music is a critical, and really fun, part of the immersive MK experience.
Boards of Canada - Tomorrow's Harvest, is my favorite. It perfectly captures the post-apocalyptic fantasy adventure theme.
As an MK soundtrack, i also enjoy: Boards of Canada- Geogaddi Burial- Untrue Burial- Kindred The Field- Cupid's Head Flying Lotus- Los Angeles Ghostface Killah & Adrian Younge- Twelve Reasons to Die Portishead- Third
This thread makes me want to make a custom board that reads each hex and, when your hero lands there, changes the music based on what is there. Chips in the tokens and board as well as the mini, all connected to a computer. It'd be nigh impossible but awesome none-the-less. Land on a village, queue village music. Approach a rampaging monster, queue the battle theme!
Incidentally, due to my screen saver, I hear a lot of World of Warcraft music when I play (mainly from Wrath of the Lich King - I have a sick obsession with a lot of the music from that expansion). I don't play WoW anymore - just love my Howling Fjord animated screen saver.