I just wanted to say i saw one in a magazine that was underneath a quilt. the gray one beneath looks like the edges were never finished. you can see stitching and raw fabric all the way around. interesting. I did cut off some border on a king size one i made because i no longer have a king.
test out fabrics by laying the quilt flat and putting some you are considering for borders next to it. that will help. fold the width you may use. Good luck!!