How do you plan to applique them down? If it is a satin stitch or similar you will want a stabilizer behind the background fabric to prevent tunneling. If you are doing a more open stitch like buttonhole, you probably won't need a stabilzer if the background is starched. If you feel that you want to use a stabilizer then a tear-a-way or wash away would be okay. I don't think you would want any more bulk to remain behind the blocks to make quilting difficult.