Change the Ubuntu 12.04 Login Screen Using Ubuntu Tweak

In Ubuntu 11.10, when you logged into your computer, or changed users, the login screen looked pretty much like this.
Standard Login Screen
With the decision to start using LightDM as the login manager, it was very simple to change the login screen background. We wrote about it in this article.
All you need is a simple text editor and a new image. We also wrote about a program called Simple LightDM Manager, that let you accomplish the same thing from a comfortable GUI interface.
In Ubuntu Precise Pangolin (12.04), released only recently, the login screen is changed automatically, depending on your wallpaper choice. This is nice in one regard, as your login screen will always match your wallpaper, leading to a consistent experience. Of course, not all wallpapers are great login screens. However, because of this change, we now need a new method to change the background screen, as the configuration file we edited in the first method is no longer there, and Simple LightDM Manager has not been updated in months.
Fortunately, one of the new generation of tweaking tools – in this case Ubuntu Tweak – is up to the task. Here’s how to go about installing it.
First, head to the Ubuntu Tweak website.
Ubuntu Tweak Website
Next, click the large silver “Download Now” button.
Click Download Button
This will start the download of a .deb file which we can install manually. In our case it downloaded to the Desktop.
Deb File On Desktop
Now we’ll open our Terminal to install it.
Open Terminal
Type sudo dpkg -i ubuntu-tweak_0.7.0-1~precise4_all.deb to install it.
Install Ubuntu Tweak
Note: the exact name of the file will change as Ubuntu Tweak is updated, so be sure to use the name of the file you download, and don’t simply copy and paste our command, as it may differ from what you have. You will also need to use the full path to the .deb file, unless you have used ‘cd’ to change your working directory to where the .deb file is located.
If necessary (there is the possibility Ubuntu Tweak needs a library not already installed on your system, which would produce errors during installation), type sudo apt-get -f install to complete the installation by installing any missing libraries.
Now that Ubuntu Tweak is installed we can launch it from the Dash.
Open Ubuntu Tweak
It will open to the main overview screen.
Main Ubuntu Tweak Screen
To change our login screen, first click the Tweaks tab.
Open Tweaks Tab
Now click the Login Settings entry.
Open Login Settings
To gain access to the settings (you’ll need to be an administrator), click the Unlock button at the top of the window.
Click Unlock Button
Now enter your password if requested.
Enter Password
To change the background image, click the image thumbnail that represents the background image used on your login screen.
Click Background Image Thumbnail
Now select a new image.
Select New Background Image
When you’re finished, simply close Ubuntu Tweak. Your new background image should be ready to use immediately. You can logout to test this.
New Background Image
One thing to note about this solution is that – unfortunately – it is not persistent. The next time you change your Desktop wallpaper, you’ll find that the login screen background has been changed to match that image, instead of what you just selected. Still, if you don’t change wallpapers too often, this is a solution for the moment, if not a perfect one.