I'm wondering how I would go about changing the default logon screen (just the background) in Ubuntu 12.04. I can't seem to figure it out.
A solution I found to work is to replace the default background being used by
> sudo cp /path/to/image.png /usr/share/backgrounds > cd /usr/share/backgrounds > sudo mv warty-final-ubuntu.png warty-final-ubuntu.png.old > sudo mv image.png warty-final-ubuntu.png
This, however, is just a workaround and probably not the best solution. It is just the most direct way to do it assuming you don't need the default Ubuntu wallpaper.
EDIT: Also make sure that you set your image to have the same owner and permissions as the original warty-final-ubuntu.png (root,755),