[puntloos]

[update] Fixed it. For some reason I had to reboot kodi before the settings worked.

How to do Artist Slideshow:

Current Kodi version: 17.3
Current skin: Aeon Nox 6.0.1
Installed Artist Slideshow 2.0.7 and Artist Slideshow helper
Enabled fanart.tv (generated API key) and music db as well in the Artist Slideshow settings
In music settings (while playing, hit select, then choose the cog) I set background to Artist Slideshow