If it were me Rainbow, I'd do some quilting in that 5" border. That seems to be a pretty large area to leave blank. There are a lot of pretty border patterns out there and that would be a fabulous place to show off some of your quilting, whether you're doing it all on the machine or mixing it up with some hand quilting! If you want to machine quilt the whole thing, you could do some simple free-form leaf motifs along the border. Those are fairly easy and quite showy. :) Or just sew straight lines on a 45 degree diagonal (maybe 2" apart?) going out in either direction from the center out to the corners. It wouldn't have to be anything too complicated since you're doing a sitd in the center of the quilt. :)