Where would I find the lockscreen wallpaper?

I am trying to change the lockscreen wallpaper – the one that shows when I open my laptop and i am prompted to unlock. I am aware of how to change the lightdm wallpaper but I don’t believe it shares the same directory.

what lock screen you are using would be the question… eos-i3 has no, and if you are using an old setup it will be in i3 folder under .config at your users home…