First let me say that I love your quilt and I think a grey binding would be perfect, or even a 2" border in grey with the same grey binding. I have made a lot of wall hangings since I began quilting and personally I like using Warm & Natural cotton batting, so that the wall hanging hangs better and straighter. The quilts I've made with polyester batting doesn't appear to have the same stability and tends to ripple. That's just my personal experience.