First of all, I'm a huge fan of double borders, the inner one more narrow and the outer one more wide. (Think of the matting around pictures.) I agree with a narrow inner border using the dark brown. For the outer border, tho, I'd stay with the "squares" motif you've got going rather than switch to another (tho piano keys wouldn't be awful). Perhaps do a checkerboard border using the red and cream tones. (Wish I had a photo for you.) Then bind the quilt with more of the brown.