From a design standpoint, the best way to keep the quilt as a focus in the room, (after all you did paint to go with it), I would find a solid spread in a co-ordinating fabric and use it under the quilt. Even if the quilt only covers the top its ok. Or you could sew up what we used to call a blanket cover.( Single layer of fabric with felled seams) the size of a spread to cover down to the top 3 inches of the box spring, and make a dust ruffle in the same or co-ordinating fabric, depending on how busy the quilt is and how comfortable you are with multiple fabrics/prints in a room. I used to get requests like this a lot from clients who wanted to retain a treasure in the bedroom. This takes it out of the realm of making do, or masking a problem and places it squarely into the I intended this as a design. :-D