How to put a whole png image as an overlay

I really need a png image which has some blurry white lines on my screen when I play games on Bazzite in steam. The reason is that my TV has some faint dark lines. The TV is LED so its not an OLED banding issue. The white lines should cancel them out to a degree. The lines make bright skies in games a pain to look at.
Now how do I do this?
Like a picture overlay when I open Mangojuice/mangohud overlay would work. But how to implement it? Its bugging me alot, ruining some beautiful scenery in games.