I actually called someone on this at work a few days ago. I work for a host, so while I do see enough adult sites while doing my job, it's not something I tend to linger over, or even view if I don't have to. In my case, asking why every time I walked past someone's desk I saw someone's butt or vulva seemed to do the trick. In a public place I think I'd be inclined to do the same. If revealing a certain body part on a person is inappropriate in a certain situation, showing a jpeg of the same part generally isn't appropriate either.