The WTFPL is a very permissive license for software and other scientific or artistic works that offers a great degree of freedom. In fact, it is probably the best license out there. This site provides information on how to make the most of the WTFPL.

You also will find a huge collection of images, vectors and sounds with WTFPL license here

https://commons.wikimedia.org/w/index.php?title=Category%3AWTFPL&from=0