Since you fused on your appliques, what type of stitching are you going to do with the appliques?? Are you going to try to do a hand stitch buttonhole stitch to keep your applique attached to the quilt top?? I think your design looks fine. If you are new to quilting, I would use a quilting thread that matches the color of your background fabric. I think you have made a very beautiful quilt that you should be very proud of it!!