I don't know. By this logic ("Who's to say what is art and what is not art?") even my pictures of stick figures can be considered art. Except that no, sorry, they're not art, and I'm not an artist.

Roy Lichtenstein asked himself "What is art?". And when he took pictures out of instruction manuals and newspaper advertisements (and, later, comic books) and reproduced them on canvas he said "Ok, I took something mundane, something mass-produced, something you see every day all around you, and I reproduced it here on canvas, using tools and techniques that artists use, I painted each of the Ben-day dots by hand, and is this now somehow not mundane? Is it now art?". And when I see one of his pictures a voice in my head says "Yes, this is art."

When I see a canvas painted black (or a shark in a tank, for that matter), that voice says "no".