Soon, you will have a lacy 'net' of squares. When sewing rows together, sew first from top to bottom, then from bottom to top, etc. This will keep it from becoming lopsided. You can use your creation as is or as a background for appliqu . Floral appliqu looks wonderful on these backgrounds.
Silhouettes also work quite well.
Stand back, look at it and decide for yourself. Often, you'll be so fascinated with the effect that you might want to leave it as is. Choose a border that compliments your piece and doesn't compete with it. Remember, you are 'framing' your artwork. A plain border usually works best.