I recall the Freelancer demo has some decent themes that never made it into 1.0, may be worth checking and see if there's something that is up to your standards (Kepler already has themes from that demo, there's still more stuff worth putting into Disco).
If it is especially Freelancer theme you seek, I would say use Q-Factory's albums called "Music for Film & Television 2A-4A" since thats where the Liberty and Bretonian music comes from, but those guys are very copyright prone