ssh into volumio
sudo nano /data/configuration/miscellanea/appearance/config.json
there are two sections that you need to edit “background_title” and “background_path”
leave the .jpg in place when editing “background_path”
You have the choice of
aurora
berlin
borealis
cymatic
darkness
eleventhhour
galaxy (which is not a galaxy lol… its a nebula)
jazzfest
morning
myvinyl
stars
Write out ( ctrl o ) then exit ( ctrl e )
reboot volumio and refresh your browser