I love the visual impact of this quilt! From your photo it looks like the only place you had a slight problem with seams matching is along the yellow stripe. don't know if your machine has any decorative stitches, but what I would do is a decorative stitch along both the seams of the 3 long diagonal pieces (the 2 corals and the yellow). Then go with something curvy as ckcowl suggested, I would go with a meander. You will have to quilt something inside the stripes in addition to the decorative stiches to secure the batting.