Beautiful quilt!
I would add a small dark blue or red border and then use that same color as the binding.
Reason being - it will make it stand out more as mentioned above it sort of fades out against a wall.
Also because a border will hold all your end seams together for when you quilt it, or have it quilted.
If you don't put a border on it make sure all your end seams on the piano key pieces are secure before you quilt it. You can do this by running a seam along the edge about a 1/4" inch in from the edge when not using a border.
Have fun and have a Merry Christmas!