I mean, white and black (even off-white) are the definition of neutral, and your wood doesn't seem limiting either. I'd think you have plenty of options for stone or glass or ceramic. What looks do you like? In what way are you hoping to "pull it together" via the backsplash? You could do cream, and bring in a bit of texture or shine, or you could do a color for accent, or a pattern...
I think you'll be ok -- just pick something you like, but I think tile will serve you better than stone.
Q