how to change log in screen on macbook air ? (NOT WALLPAPER(

i’ve been trying to change the log in background of my mac but no matter what i do it stays on the orange / blue ventura background. i always shut down my laptop & whenever i turn it back on , the log in background that i tried choosing never stays & it’s so annoying. is there a way for me to change it ??? i hate seeing the orange screen when i log on to my laptop