When Windows 7 or Vista is joined to a domain you get the "ctrl alt delete to logon" screen, it is designed that way because of security reasons, imagine a domain of 100 users or even 50 users and there user pictures are displayed onto a domain joined pc ?
There has been alot of threads and people asking / looking for this feature but it isn't available, unless some third party tools (which I am not very well aware off), you can change the background but the logon pictures go away when you land on the Login screen after a reboot. they can be seen when a user locks the pc and then presses ctrl alt delete to logon / resume there session again.
There are GPO settings, which makes the login screen forgets the last username etc and settings to set a default domain to logon to.
Unfortunately, what you are after isn't possible as it isn't supported from Microsoft.
Hope that clears - let me know if you have any more questions on this.
Kind Regards
http://windows7forums.com/windows-7-graphics/16835-how-display-domain-local-logon-accounts-logon-screen.html
http://www.google.co.uk/search?q=login+screen+windows+7+domain+joined&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a
