Log-in screensaver

I have Mojave 10.14.6. When I turn on my computer and the password screen comes up, there is a picture behind it. If I click on my icon, the picture changes to something else. If I leave the password screen up for more than 30 minutes a screen saver starts. The problem is, none of the pictures or the screen savers are the ones I have chosen for my computer. When I log-in, my wallpaper is correct and if I leave my computer for more than 30 minutes the screen saver I chose begins. I cannot figure out how to change the log-in picture or the screen saver. Any suggestions?

Thanks

Cynt