I agree about "the dark block". Love the idea of it as an accent pillow for the bed.
I think the Piano keys border would be great. I might add a small 2 inch border to stop your eyes, then make the piano keys a bit larger--like 4 inches--IF you have enough fabric.
I had to laugh about the white duvet cover. We have a white quilt in the top of our closet. It got to the cleaners and put into a bag when we had kids--ummmm...17 years ago. :lol: