We’ve got two different solutions for you!

How to change lock screen picture on Xiaomi Mi5

First method:

If you want that lock screen wallpaper to be the same as main screen background you need to do the following:

  1. Follow this path “/data/system/users/0”
  2. Delete “keyguard_wallpaper.” file

If you want that lock screen picture to be different from desktop background, follow these steps:

  1. Select the background picture and rename the file to “keyguard_wallpaper” without .JPG file type.
  2. Move & replace file in /data/system/users/0

Second method:

  1. Install theme.
  2. You should see theme background on lock screen.
  3. Place the picture you want on main screen.
  4. Go to the themes > Lock screen background
  5. Select “System”

Now you should have the same background on both screens.