When accessing DoD computers they make it look all secure like, so being the trek fan that I am, I created something that looked like something I'd find on a DoD logon screen, complete with modified security disclosure at the bottom.
Currently, it's the logon screen on my Windows box and I set it up that way with directions from this site (Windows 7 and Server 2008 R2 only):[link]
This works in Mac too:[link]
I've written it in 1920x1080 (for my 42in LCD) and 1920x1200 for my MacBook Pro.
I have absolutely no clue how you'd make this your logon screen for XP/Server 2003 and Vista/Server 2008 (yes, there is a difference between Server 2008 and Server 2008 R2)