As seasoned readers may know, I have always been intrigued by the beauty of math. (See here, here, or here for some examples.) Now that my job title is S.T.E.A.M. Master Teacher, I have been looking even more for ideas on how to integrate math and art.
Math Craft is a great place to start. From mathematical knitting to Sierpinski Christmas trees, there is no shortage of inspiration on this site (though it is a bit heavy on polyhedrons). Not every post gives you instructions, as some of them feature work by professional artists – but you could always pose the question to your students, “How do you think they made this?” They may end up making something completely different, but equally as beautiful, along the way.