IIRC, the reason lots of old paintings gave cats weird faces was because the artist was trying to indicate that the cats are mischievous. Basically, dogs got painted accurately because they follow directions. But cats got painted like jesters on purpose, because they just do whatever the hell they want to do; fuck your rules, fuck your family’s nice dishes I’m knocking this shit off the shelf, feed me and tell me I’m pretty while I bite you for scratching my back wrong.

The weird faces are symbolic, and the audience at the time would have recognized the symbolism. Cats were also heavily associated with witchcraft and paganism, so it could also be used to symbolize that link. Like if a cat is painted looking demonic and/or standing on two feet, it could be possessed by a spirit.