Adult amateur art covers a wide range of mediums. It can be created in photographs, videos, paintings, charcoals, sculptures, and the list goes on. What one person sees as art, others may see as simply porn. The definition of art is as diverse as the methods of expressing it. You can have a simple photograph of your partner nude and using some computer software, make subtle changes to the colors and consider that art. Perhaps a basic sketch of a girl about to suck a cock from some unseen guy is your masterpiece. Or how about a paper mache sculpture that you glue a picture to. These can all be considered amateur art. The underlying theme would be that they are produced by someone that is not a professional artist and they all have a sexual theme that is appreciated by at least the person who created it.
With that thought in mind, everyone who takes out a camera and tries to take a picture of their partner in some sexual situation, whether a simple nude to some provocative poses, whether it would considered softcore or hardcore, is producing some form of adult amateur art. So break out those cameras and canvases, let your imagination take over, grab your partner or do some solo work. Have some fun while you do it. Either way whatever you create is sure to be looked at from both camps, after all, art in in the eye of the beholder.