No photo in Desktop Pictures folder?! I'm trying to change my lockscreen

HELP!! I want to change my lockscreen om my Mac Air (m3) 2024, separately from my desktop screen.

I have done the whole finders -> go til folder -> /Library/Caches/Desktop Pictures/ -> and dropped an png photo, but the thing is, that there was no photo in there to begin with?

In alle the videos I saw, of how to change the lockscreen, there would be a photo in that folder, that I had to swap with a new on, but on my Mac, the folder was just empty??

My Mac is updated to the lasted software, I have tried to restart my Mac, I have tried to set a different background, and see if that did anything, but nothing is working!

Plz help