I'm envisioning wide strips, like 12" or so, cut from the width-of-fabric to get the full spectrum, alternated with black strips for a really super-quick strippy quilt! Or standard-size Log Cabin blocks arranged in color progression as they're cut, to make a nicely-blended rainbow... There's a LOT you could do with that for a top, without losing the punch of the terrific dye job. I agree that it's way too good to be hidden on a back. :)
Love the dog sacked out in the first pic, by the way. ;)