On 2019-04-07, Andrew Clark <ajfclark@gmail.com> wrote:
>
> What am I missing?
>
It appears the wiki's wrong and has been wrong for quite a while now (if
not from the very start).
Maybe the following method might work (it seems like an incredible
rigamarole for such a trivial user customization, but there you go).
https://wiki.archlinux.org/index.php/GDM#Log-in_screen_background_image