OLED wallpapers means images with large percentage of true black and/or saturated palette.
OLED pixels are turned OFF when image pixel is true black, and that way it not only looks great, but it uses significantly less battery.
And saturated color pallet with several colors, as OLED displays such color very nicely, much better then IPS display.
If you use such image as a wallpaper on for example IPS display, it will look WAYYY WORSE then on OLED display.
you autistic idiot.