(There’s a similar thread, but problem seems different.)

I can set a system wallpaper (bg) image, BUT LL desktops always seem to appear over the ‘grout line’ between image tiles. (Cropped to screen size, and set as ‘fixed’.)

The only workaround I’ve found, thus far, is setting wallpaper (bg) image, per wallpaper of LL setup. This works flawlessly, but is less efficient, as it must be set separately for drawers & each LL wallpaper.