Factum est.

Slim now displays another background instead of the default but it is
still one of golinux's creations. I find the previous simple
backgrounds better suited for a display manager. This one is dark
purple with Devuan's logo across the screen. It is
/usr/share/images/desktop-base/your-way_purpy-narrow-large.png.

Nice and simple, the way I want it.

Thanks to all.