The most beautiful part of being a linux user is the choice you have, whatever issue it is. Like any other Linux distro, Ubuntu is infinitely customisable with any number of themes and applications. This include login window themes or gdm themes as well. Major source for themes in ubuntu include www.gnome-look.org and www.deviantart.com. There, you could obtain literally thousands of good quality themes.
And i think may be that is the problem. I am not saying it as a bad thing but still, you are simply overwhelmed by the sheer number of choice you have. Here is select set of login window themes that i think are really worth a look. If you are looking for full set themes which include gdm themes, wallpapers,icon themes etc you may want to take a look at 10 beautiful themes you can download directly from Ubuntu repository.
Note: Some of the screenshots below may not be appropriate for all. If you are below the age of 18, please refrain from going any further.




RoMuDsGr_PacificBlue GDM Theme



Dead Rising Night GDM Theme - Trust me, this one is scary


Bielefeld City Lights GDM Theme




Discrete Crunch Bang GDM Theme







How to install GDM Login Window Themes in Ubuntu
- Goto System > Administration > Login Window and select the tab local.
- Simply drag and drop the downloaded tar.gz file.
Disclaimer: Themes above is not owned or connected anyway to Ubuntu Manual. I have provided the links for each theme in their respective titles. If you like the theme, i strongly recommend you to visit the link and leave a comment(at least).




Thank you sir,
I'm new on Ububtu and I've some problems with it
How can I use thid walpapers as Log in
Very nice!
Thanks for sharing. And no haven't seen none of them bevore ;)
i also use the FBI, CIA and NCIS ones their fun too.
FBI
http://gnome-look.org/content/show.php/FBI+Login?content=49544
NCIS
http://gnome-look.org/content/show.php/NCIS+Login+Theme?content=104726
CIA
http://gnome-look.org/content/show.php/CIA+Restricted+Access?content=110...
Linux noobs think your hacking if they see u logging in :)
Thanks for sharing those themes with us, keep visiting :-).
Very good!!!
I don't use neither Gnome nor Ubuntu but I've to say.... WOOOWWWW!!
Thanks for sharing, linux isn't just for system admin, linux isn't just black and white screen, linux can beautiful and pretty but still powerfull and secure.
Good stuff. I think one of my favorite GDM themes is the default Linux Mint 7 one. Keep up the great posts. I'm adding you to my Teh Google Reader right now. ;-)
you are welcome friend, keep visiting :-)
heh - time to change my login screen.
"Dead Rising..." :)
"Dead Rising" is wicked indeed ;-)
Instead of www.devianart.com must be www.devianTart.com
Thank you i have corrected it. :-)
charming post. :-)
Some really cool stuff man! I got the one that tells everyone to "fuck off"!! He he he he! Nice site btw. Cheers!
Thanks dude.. btw, that gdm is my favourite too ;-)
keep visiting or subcribe to our twitter account.
ya, use the wood one as well +1
Your website keeps on poping up in google ;) and I'm always surprise with the quality and usefulness of reading your posts. Thanks
Thank you for those kind words. Hopefully will produce more quality articles in the future. Keep visiting. :-)
Thanks for the post, especially love the wood one...
I´m use Leaf GDM Theme since 2008