Personally, I would not consider Minky for that size of a project. I love your quilt and the fabrics you've chosen. If it were my quilt, I would keep the back a lighter color -maybe a 2 color print, white and whatever (I would go for yellow myself, but I love yellow). Can't comment much on the actual quilting, but I think an all over pattern as you have shown would be fine. You could also go with flannel on the back if you want that cozy feel.