I don't understand using an "ugly" fabric (what you personally intensely dislike) for a backing. It's half the quilt. And it's not like a backing "hides". Sure, it doesn't take center stage, but it is an integral part of your quilt. The saying "don't decorate around a disaster" comes to mind.
But if you really DO want to salvage it, you might try a couple fat quarters from the same line that appeal to you.
Or cut it up into large practice pieces to practice your FMQ.
Or resell it here. You'd take a loss, but someone else might consider it a perfect gain to their stash.
I've never found a fabric "grow on me" if I hated it from the get-go. Color is something we have an emotional response to, and it's hard to explain. Sometimes we just have to face disappointment and sing a little tune..."let it go, let it go". Haha.