The elements are used as a theme in lots of artwork, so why not carry it over to crafting?
Elements as materials/processes- make something out of clay for Earth, windchimes for Wind, fire polish some beads for Fire
Elements as representations - make three different collages or crafts which represent personalities or other things you associate with each element- a yoga mat Earth, a keyhole scarf for wind, a tank top or sexy red dress for fire
Elements as color schemes- simply make something with Earth colors, something with pastel colors (Wind), and something with reds, oranges and yellows for Fire.
Other elements could be used, too, like the real ones on the periodic table, or more proverbial elements like the ones above, too. This challenge could be interpreted in so many different ways, so that it allows for a lot of creativity.
What do you think ?