These remind me of mandalas. We could get stones and do mandala zendoodle art on them, and then write a simple encouraging message on the back for baby girl. Make a nice fabric bag for her to keep them in.
DIY hanging diamond decor by contributor Kathleen :: These use straws covered in silver muffler tape. She used cotton string, but fishing line works, too. All the dimensions for the straws are given for all 3 sized diamonds!