While it often gets over looked, artists have a long history and tradition of upcycling materials into their works. One of the most popular methods for doing this is bottle cap portraits
but of course there are all kinds of art that make use of upcycling, including art installations from all over the world, such as this shadow art made from what is otherwise a simple pile of junk
Now while most people aren't going to ever want to make an art installation centered around using upcycled materials in the piece, it does help show the extent of which it's possible, and some of what you can do at home. Maybe put a small bin in your house to collect bottle caps to start making art with.