What a lovely quilt! I love your color choices for that pattern. If you feel you need to do more quilting, then by all means...do it! I'm not sure I would use any thread color other than to match your background. You want this quilt to be carried by your piecing and the design, not the quiltng design.
Oh....all these opinions...we all have one. Whatever you decide will look perfect as that is a beautiful quilt!