Looking for art that has a Creative Commons licence, is a way to find this kind of free art. eg. Search for: ‘creative commons pictures’

Here are a few links:

Pictures

Unsplash.com

www.flickr.com/creativecommons/

Video

vimeo.com/creativecommons/

Music

Jamendo.com

freemusicarchive.org/home

creativecommons.org/legalmusicforvideos/

Comics

peppercarrot.com/en/webcomic/ep01_Potion-of-Flight.html

perthfreeculture.org/comics.html

There are many more out there, you can use the search method above.