LightgreyGDM is an "unofficial" Gnome Display Manager Theme made to fit with the LightgreyV2 theme suite by sixsixfive --> http://sixsixfive.deviantart.com/art/LightGreyV2-GUIKit-117381124, but of course it can also be used with other minimal themes.
LightgreyGDM is just a simple modification of Login Concept 1, by CITguy --> http://citguy.deviantart.com/art/Login-Concept-1-GDM-Theme-111148546, so almost all credits go to him, i've just changed colors!
LightgreyGDM is highly customizable: for example, you can change the default "XUBUNTU LOGIN" text. To do that, simply edit the LightgreyGDM.xml file changing "XUBUNTU LOGIN" to whatever you like.
I hope you like it, enjoy!