I want my desktop background to also be the background for the greeter so I type this into terminal
sudo cp /home/luke/Pictures/Wallpapers/starfish.jpg /usr/share/backgrounds/
the copy works fine, however when I go to backgrounds the thumbnail is a question mark and the photo cannot be opened nor set as the background.
To troubleshoot I typed in
gksudo nautilus /usr/share/backgrounds/
and voilà, the photo has the correct thumbnail, and is able to be opened with a double click.
How do I get this problem to go away? I copied the exact same wallpaper to the exact same directory on my laptop and set it as my wallpaper (and greeter background) with no problems. Why won't it work on my desktop?