I would use white thread to quilt snowflakes of all different sizes around the appliques, with a larger one in the space where four blocks come together. If you do a search of longarm pantographs, you will find several very pretty snowflake designs you can use, even if you don't have a longarm. They can be quilted individually by FMQ, or however you choose by hand. I think you are going to have to do some stabilizing quilting within each appliqued snowflake, in the tiny spaces between applique pieces. Your blocks are absolutely gorgeous!