I haven't yet read the whole article, but I immediately find it fascinating - I grew up in the UK and these images are familiar, they were in country pubs and occasionally people's houses.
It never occurred to me to ask why!
I guess I assumed the images were old, and someone wanted to show off that they had a particularly spectacular cow. And the author is right, so many of them are side on and rectangular.
I wonder how many other things in the world that I've ignored as basically wallpaper actually have a backstory...