> until the 19th century, ads were basically just information dense textual statements.

I'm curious how does this account for "town criers" and the like? And there seems to be quite a few examples of less "information dense textual statement" in some of the articles on Wikipedia about advertising [1] [2].

[1]: https://en.wikipedia.org/wiki/History_of_advertising [2]: https://en.wikipedia.org/wiki/Trade_card

I'm not an expert, but looking at those articles, most of the illustrated and colour designs seem to have become popular in the 19th century, though I do see a few illstrated examples from the 18th century as well.