Cannot change desktop background in new Yosemite OS

I tried this and it does not work for me. I can change my background if I select a new picture and then log out or restart my computer. New picture comes up at login and hold for about one minute until reverting to previous background picture. I have deleted the previous background picture in iPhoto,Photos and the cloud. I created a test user and the functionality works fine as it does with a guest user. I reinstalled OS X Yosemite with the same results. Any suggestions?

***, same issue here caused by Pathfinder6.

The way I got this to work was by putting the photos I wanted to use, into the Desktop Pictures folder (within the Library folder) on the hard drive.

I tried what you said. It still disappeared after shut down and re-start.