My MacBook's background is messed up and won't change now. How do I fix it?

Question

The background on my MacBook Pro has always done what it wants to. It especially likes to change itself back to the standard OS background every time I shut the computer down, but that is besides the point. There is now a bigger issue I was going in to show a NEW Mac user how to change the background on their new iMac, and as soon as it opened the window, the entire background is now gone and nothing but a black background is there. I tried to change it to something else, and nothing. I tried using a picture like usual, and nothing. It reflects n the window that that picture should be the background, but it is not showing up as the background? What in the heck is wrong with this thing?

Answer 1

Back up all data.
In the Finder, hold down the option key and select
          Go ▹ Library
from the menu bar. From the Library folder, delete the following item, if it exists:
Caches/com.apple.systempreferences
and move the following items to the Desktop, if they exist:
Application Support/Dock/desktoppicture.db
Preferences/com.apple.desktop.plist
Launch System Preferences and test. If you still have the issue, put the items you moved to the Desktop back where they came from and post again. Otherwise, delete the items.