There are. There is historical documentation of these things being used as objects of arousal.
I'm going to put emphasis on your 'more'. Yes, sexual domination was a symbol of power, at least to the later Roman people. This is partially due in part to early paganistic Romanii beliefs that the goddess of fertility (and in some sects the Goddess of the home or hearth as well) was the most mighty of gods and also the most stable of gods for private worship. Dominating one sexually was almost like a writ of ownership being presented to the gods. Does this make it less pornographic? No, not at all. Romans still told stories, sang songs, and enacted plays that were highly erotic for the purpose of eliciting sexual arousal from the crowd. There was no better way to get a Roman official on your side than make a product that aroused them.
You actually argue against this point yourself with an earlier quote. This here:
You are arguing from a modern perspective of what is acceptable when it comes to pornography. Unlike modern times, privacy was not as readily available and art (regardless of whether it was pornographic or not) was even less available than that. Art of any kind was difficult to produce and circulate, until the invention of the printing press. That is, in fact, why art was typically public and, if it was not, was only owned by the wealthy. To judge whether something was sexually explicit material by modern cultural standards is silly. What we do know, though, is that cultures through history both revered pornographic art and revered the act of masturbation, both being seen as positives.