Realism, Abstract and now: Metamorphic Art.
Metamorphic art is imagery that has the appearance of something real, or suggests something real, but is actually created by a process that is unrelated to the real imagery and only bears a resemblance to real things by accident.
The best examples of metamorphic art are fractals which often look like and are described as real things, usually plants or other organic structures, but the resemblance is only accidental. Most algorithmic art or generative art programs create metamorphic imagery because the underlying process is one that can only produce abstract or non-representational images.
It's really just a matter of process. If the process of making "imagery" is not human (or photographic) it is extremely unlikley, if not impossible, for it to reproduce the human form or face or anything else that already exists. In fact, only human artists (or photography) can reproduce real things because that requires intention and very complex thought processes.
Computer programs or natural processes (landscape, rocks, but not biological processes) create new things; things that are unique. However; we often select the products of these processes (eg. fractals) that look like something real because, I think, we find realistic imagery to be more interesting and expressive.
Abstract is the category this sort of art would be placed in for the sole reason that it's obviously not realism like a hand painted portrait or landscape would be. However the realistic "context" that the imagery is placed in makes abstract an awkward category.
The study of Geology defines three types of rocks: Igneous (original rock cooled from molten material); Sedimentary (rock made up from the erosion of other rocks); and a third, composite type which is produced by heat or pressure acting on the other two types and called -- Metamorphic -- simply meaning "changed".
Similary I would suggest that there is a need for a third type of art classification in addition to realism and abstract. Computers have turned the production of non-human imagery from what was previously a narrow stream into what is now more like a river and trying to speak and think about this imagery as a type of abstract art or even as some sort of anomaly or curiousity and "non-art" limits the study and appreciation of it because that's not what it is.
Metamorphic Art: "I don't know what it is, but it looks like something."
The second image was made in Capow2007 using the standard Cellular Automata option. The first image is just a negative (inverted) version of it. Both are 2-color images which makes for stark contrasts and small file sizes.