Once in a while an artist would attempt to portray something out of the ordinary that was seen in the sky such as comets, meteorites, or odd weather happenings. There were also a large number of common, standard symbolic elements artists would incorporate into their works -- solar and lunar spheres with wings, beams from the sky indicating communication with the divine, etc.

They'd also use a little something called their "imagination" to depict all sorts of things like boats or people with wings flying about. These aren't photos. They are artistic interpretations, many created way before artists realized that their artwork should or even could be an accurate representation of something.

As a result, it's very difficult to equate these things directly with UFOs as we know them today, as possible alien spacecraft.

However, if you can provide some kind of corroborative documentation to show that the artist was, indeed, recording a sighting of a UFO, then by all means present it.