Here’s what to do:
tap the Apple menu in the top left corner and clickSystem Preferences.
Next, opt for profile icon.
It will be previewed in the bottom left corner.

Login screen on Macbook.Stocksnap
you’re free to customize some images.
The options to customize are along the top on the right side.
When you’ve got the login image you want, clickSave.

Your new login picture will appear next to your name.
Changing your Mac login photo also makes the same change on other Apple devices.
The login photo is actually the photo that’s connected to yourApple Account.

So, you’re not just changing something on your Mac; you’re actuallychanging your Apple Account picture.
Any machine that uses the same Apple Account as you Mac will automatically have this image applied.
This detail may not be a problem, but it’s worth knowing.

you’re able to change the background wallpaper, too.
The login screen uses the same image as your desktop wallpaper.
tap the wallpaper you’re interested in and it will be previewed in the window at the top.

If you want to use that wallpaper, pick the download icon to add it to your Mac.
Once you’ve picked the wallpaper and configs you want, they’re applied to your Mac.
sign out of your Mac, wake it back up and you’ll see the new login screen wallpaper.

Then, right-smack the drive or folder you want to change and selectGet Info.
smack the thumbnail and paste your new image.
To change your Mac login password, go toSystem parameters>Users & Groups>i symbol>Change.
Finally, kickstart your Mac.