Everyone should own Black Aria...and Donnie Darko..well I don't own it but I probably should. Dead Can Dance just rocks...creepey but not as demonic as Black Aria.
http://kabish.com/adrian/dead_can_da..._the_labyrinth I personally recomend The Ubiquitous Mr. Lovegrove from that album.
You might also look at some VAST...may be a little too rock and roll for what you're doing but he's got some heavier stuff as well.
Anotomica the String Quartet Tribute to Tool has its creepey moments...
Loreena McKennit...Not overly creepey but in the same vein as DCD
The instrumental Crow Soundtracks...
Old School Enigma...
Some of the stuff on the Samurai Champloo Soundtrack might work
((got home and looked through my cd collection))