How to create a unique welcome screen in OS X El Capitan
In El Capitan OS X users now have the ability to customize the login screen in the operating system, setting their own unique image. Not so long ago we told you how to install screensavers on a Mac with a new Apple TV, and today we will show you how to make your computer even more.
This is done easy. To begin with, we need a photo or picture in high resolution. It must be in png format, so you must first export it to this format using a standard utility Preview.
After that things are easy. Rename the file to “com.apple.desktop.admin.png” and place it on the desktop. Then open Finder and hold down the key combination Command + Shift + G. In the resulting window, enter /Library/Caches/:
Drag the file into this folder replacing the previous one.
Ready! It remains to place the computer in sleep mode/shut down/restart it to see the new welcome screen.
And then it all depends on your imagination.