How to customize the login background in OS X

Personalizing our computers is very common these days, and adding images to the login screen is no exception. For OS X El Capitan users, there's a way to customize their Mac's login background without the default blurry image by modifying a system file. Therefore, it's advisable to create a backup before making this change.

Customize the image that appears on the OS X El Capitan start screen

1. The first step is to find the image you want to use as your home screen background. It should be a high-quality image with the same resolution as your Mac's screen. If you already have the image you want as your home screen background, you can take a full-screen screenshot and save it.
2. Once we find the image, we download it with a preview, and export the image to another format, in this case .PNG, changing its name to: "com.apple,desktop.admin.png" and storing it on our computer's desktop, so we can manipulate it better.
   
3. We will press the CMD+shift+G keys simultaneously and a command window will open, in which we will place or paste the path /Library/Caches.
   
4. A window will open, and we proceed to find the file "com.apple,desktop.admin.png" and change its name to "com.apple,desktop.admin-copia.png", or use another word. The idea is that by renaming it, we can save this copy and not lose it in case we need to restore it later.
   
5. We find our saved image on the desktop and move it to this folder.
   

Once you've done that, it's ready. Log out of your Mac or restart it, and you're done. The login background will change to the one you assigned. It's a practical way to personalize your Mac's login screen—quick and easy. You can change the image at any time by following the same steps again and modifying it to your liking.