Hello AhxiuXIII,
Thank you for posting. It seems that you might be having some problems with your Pictures folder. The desktop background defaults to a black background whenever it can't find the picture it was using for the backgraound before. I would suggest that you check your Pictures folder to see if it still contains the pictures in it or whether you moved the Pictures folder. Moving the Pictures folder can have the same effect on your desktop background.
Please let me know if this helps you.
Zack
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