I don't think the backing matters just so it looks good. Sometimes they ask about 'art' on the backing. Mostly quilts are judged on workmanship, quilting, binding - thick enough and are the miters stitched down. I've found that the judges for my Guild's shows usually offer a little critical feedback and also include something to praise. If you didn't quilt it yourself make sure you indicate who did.
May in Jersey who should be working hard on her quilt for her Guild's show in May instead of hanging out online, LOL!