This is where I sell prints and posters of my artwork. I often begin with a photo from the public domain and use that to make a new image. This is termed appropriation art and is akin to sampling in the audio world. Digital appropriation artists are creatures of the Internet and a logical outgrowth of cyberculture.
I do a lot of Native American-themed art, often based on the exquisite work of Edward S. Curtis selected from the public domain. Native America symbolizes, for me personally, the natural human, the last wild and free people living in harmony with the natural world, and of course man's inhumanity to man.