Take the above image. I would probably say that is erotic art. The black and white image makes it seem more serious. But its not just whether the image is in black and white. For example,

this is in colour but I'd still say that it was erotic art. Both images have a more serious mood. But there's something different about this one

I would figure that most people would consider this to be more pornographic.
Here the model also has the thong and bare buttocks like the previous two but there's something different about the mood. This isn't as serious or somber as the other two. Here I get the feeling that she's having a good time, that she really likes showing her ass. While in the previous two the models were just modeling and used as part of a composition.
I could continue to explore these alternative viewpoints and considerations, but I'm just going to post some more pictures of erotic art.
I'll close this out with a final image that may have been inspired by the 2 Live Crew