To make my own script usable for you would require a bit too much work on my side since it's specifically adapted to my own needs. But basically you just draw an image on the splitter settings/script PerTrack tab.
$imageabs(0,0,%_width%,%_height%,path of your image,,,)
Then draw a black opacity rectangle:
$drawrect(0,0,%_width%,%_height%,0-0-0-100,0-0-0-100,)
That 100 number is alpha, sets the opacity level, change to what seems best.
Or overlay a transparent png image over it using $imageabs again. I've included some png images of various opacity and fill patterns. They are 4k size since my foobar is on a 4k screen. If you're using these either crop them to the size you need or use the image's absolute size in $imageabs:
$imageabs(0,0,3840,2160,path of your image,,,)
Set titleformat mode on startup to "follow cursor" on the script tab of the splitter settings of the panelstack where you put your $imageabs script.
Elpaylist however is a different beast. Highly customizable but very much done with scripting.