Comment 19 for bug 973993

I did a bit more digging around. I had a look at the greeter log file. I have attached the greeter log file with this comment.

    sudo less /var/log/lightdm/x-0-greeter.log

I noticed these lines:

[+0.58s] DEBUG: background.vala:67: Making background /home/mendhak/Pictures/Wallpapers/General/sunset_texture.jpg at 1440x900
[+0.58s] DEBUG: background.vala:144: Error loading background: Failed to open file '/home/mendhak/Pictures/Wallpapers/General/sunset_texture.jpg': Permission denied
[+0.58s] DEBUG: background.vala:116: Render of background /home/mendhak/Pictures/Wallpapers/General/sunset_texture.jpg complete
[+0.58s] CRITICAL: background_loader_create_pattern: assertion `image != NULL' failed

That's a wallpaper in my own wallpaper collection. It is trying to access it and failing. On a hunch, I went in and used one of the regular/supplied wallpapers that came with Ubuntu (right click Desktop, change desktop wallpaper). That worked!

I then tried to set a custom wallpaper again after doing a chmod 0777 on the entire wallpaper directory. That still didn't work, the log file still mentions permission denied. I am not sure what kind of permissions I should be setting on my Wallpapers folder.

***tl;dr: Use one of the default Ubuntu wallpapers***