JMHO: I would put a black border (fairly narrow), then do more log cabin blocks as the final border.
Either the black/piano keys or the turquoise stripe will work. Depends on how much more work you want to do!
I am a scrappy lover, too, and log cabin is my favorite block! My avatar photo is actually a brown and green log cabin with hand embroidered wildlife blocks. I also always paper piece my log cabins for accuracy.
Love, love, love your quilt! Have you given any thought to how you will quilt it yet? Can't wait to see it finished.