I think that it's interesting how we can use unconventional art materials/processes to accomplish artworks equivalent to, if not exceeding, art pieces created using traditional supplies. This challenges students to create things that are not expected and more "out of the box".
As seen in the pictures of above, it is very possible to create a work of art even more breath taking than one that uses common materials, such as paint. In some cases, such as the bust made of books in picture 1, unconventional properties adds an eye catching/unexpected element of texture and color.