I like your quilt a lot. I don't think I have ever seen a log cabin done scrappy before. I think the piano keys would be a distraction. I think I would use a black or navy border of 3 inches (give or take an half inch) and then bind it with sections of scraps. I would make the sections of miscellaneous lengths and join them on the bias. If you did this, you would need to be careful about the corners so you don't have seam joints at the corners.