Are memes a novel linguistic category of proverbs?

Hm. In this subculture, sure. Adage at least, if not proverb.

The fragmentation of culture in the Anglosphere, and the lack of common cultural reference points as a result, is a strange thing. It feels unprecedented. You can’t fall back on common literary references any more. The Anglosphere thinks traditional wisdom is old hat and values innovation; so proverbs are derided as cliches (a big difference from say Greekdom). You can fall back on pop songs and movies to some extent, but only to some extent, because of the fragmentation.

So in this culture, memes fill a function. They are visual, because the communication enables it. Maybe not completely unprecedented; there’s lots of coded memes in Renaissance painting, for example. But yeah, they’re a proverb of the future.