My take on this is that...any art that is about something, including being about atheism or depicting atheism or influenced by the concept of atheism, is actually more like religious art than not. However, art that begins in not knowing but refers consciousness to the actual Knowing itself, is atheistic art in the sense that it does not refer to religious constructs. I know that's a headfull of ideas but any artist who has listened to undivided consciousness knows what is being referenced here. Consciousness that is divided - ie: into atheism and theism, is already within a belief system and a world view and has rituals holding such a belief having nothing to do with reality at hand - ie: daily life. There are many examples of art that might qualify here in my own quirky sense of this actual intention of atheism or non-belief represented somehow as art - but not in art. Abstract Expressionism might be one. Philip Glass compositions would be another. Another way I think of this is that art that is intended to represent something is more likely illustration, not art in the first place. That's not a bad thing, but it is still illustration. Comments welcome!