Please describe the problem:
I'm able to change the background picture, but it gets unset as soon as I trash the original image file that I used for setting the background image.

Steps to reproduce:
1. download an image from the internet to Desktop
2. right click on desktop and select "Change Desktop Background"
3. drag and drop the image from Desktop into the background selector
4. right click the image file on Desktop and select "Move to Trash"


Actual results:
My background gets set to the image but once I trash the file, background gets unset again. It also disappears from the background selector making it impossible to select it again.

Expected results:
I'd expect the background to remain as I explicitly told I want it to be. Showing the image I originally downloaded from the Internet in step 1.

Does this happen every time?
Yes. It happens every time.

Other information:
I assume forcing people to keep an image file on their desktop is not intentional.