To make it bigger, I would buy more batiks and make more blocks. If you put new blocks all around the blocks that you have, they wouldn't have to match. For borders, I would use only batiks and batik like fabrics (like maybe tone-on tone). The block doesn't really lend itself to sashing strips, or interspercing with solid blocks. But you could use solid blocks with the line of the block (the blue fabric) extended through it, if you could find more of the blue batik.