I'm assuming this quilt has a lot of genealogy on it and, with the style you have chosen, I'd hand quilt this very simply. The first thing that has come to mind is to stitch in the ditch. You may need to do the vertical and horizontal seams around each block and then go diagonally to outline the snowball blocks. Just keep on going at the diagonal across the 9 patch blocks I would simply "underline" a few of the embroidered lines with quilting to highlight or secure the center of those blocks. Because of the nature of the quilt, I would keep the quilting simple so that the information is the highlight. As to borders, I'm not a big fan of black as it fades with time but a narrow strip of black and then the piece you have for the outer border would be nice. And a comment on black--if it has polyester in it, it doesn't seem to fade as cotton does.