Call Manson and have him and Spooky Kids redo all of Disneys classics soundtracks unless that is too dark for you
Trent Reznor does some great weird stuff too for clock works and creepy music. But I have to agree that Elfman is perhaps the best realistic odd music composer. Edward scissor hands for example.
I know Manson made the soundtrack for the 3D adaptation of Burton's Nightmare Before Christmas, which could be used for Grimm, but i don't know what it's worth. I don't know the Trent Razor's stuff either, but i will look for it.
I have made some researchs and found some other classical pieces which (i think) will be wonderful for Grimm :
- Charles Valentin Alkan : Aesop's Feast
- Edward Krieg : In The Hall of the Mountain King
- Modest Mussorgsky : Night on Bald Mountain, Gnomus and Baba Yaga's Hut on Fowl's Legs
- Camille St Saëns : The Carnival of the Animals
- Richard Wagner : Siegfried Funeral March
We're nowhere near Manson or Trent Razor here, but it's beautiful, dark and epic, and i think it will work great with Grimm.