LightDM GTK Greeter Settings will be fully integrated in Ubuntu MATE 15.04 and is a Control Center applet to tweak the LightDM theme. You can change just about every LightDM GTK Greeter option, including changing the login background image which is a frequently requested feature.
I've used the existing lightdm-gtk-greeter-settings build recipes to make everything you need in a PPA.
If you are feeling brave, let the destruction begin
I am using 14.04 and I didn’t have any luck with the greeter avatar settings that I downloaded. The image would show up on fine on the settings, the saved button would turn grey, but I still got a standard avatar when I went to the login screen. I did get it working using the AccountsSettings method on the Arch Wiki. This is the computer that I was having trouble with earlier as far as the greeter settings are concerned, so the problem might not be true for other users.
This dialog is a welcome addition! In using it, I found there is a small error in the "Window position" tab. The Vertical Position description should read "from top" instead of "from bottom". The origin of the coordinates is at the upper left corner. Please see the screenshot where I set mine to 40% on the vertical scale.
I'm using 15.04 alpha 2. Thought you would want to know about this!
The problem here is that there are actually check boxes in this dialog that are not showing up depending on the theme being used, causing misinterpretation. I see the same problem in some other themes. Other dialogs will have the same problem - I see it in Synaptic Package Manager, and Audacious Playlist Manager as well. Here is the same dialog after changing to "Ambiant Mate" theme - big difference!
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