As for paintings... there was really zero information on the site other than pictures of paintings? Nothing about the artist, the size, or the price? You apparently don't realize that a lot of people who rely on screen readers are able to see to some extent. They may use the screen reader to navigate your site or make purchases, but they may still be able to see the paintings (sometimes by magnifying the screen greatly and looking closely at the details) if not in exactly the same way that you do.
I don't disbelieve that shakedowns like you describe happen. But there is a reason for the rules that you are apparently breaking. It also sounds like you don't really believe that disabled folks deserve any consideration.
You say you don't hear from them, asking questions or complaining, probably because the vast majority just give up when they encounter websites like the ones you create. They are likely very tired of contacting website owners (assuming they can figure out how to do so--not easy if the site isn't accessible!) who send back insults about how they can't possibly be interested in the contents of the site or accusing them of trying to shake the website owner down.
The sort of thinking you are putting on display here is exactly why the ADA is so important.