Update of GMail Dark - Gmail Dark-Grey No-Nonsense by Julius B. Thyssen, fixing some minor annoyances, adding black borders (like the blue ones when you use GMail normally) and adding a more eye-catching highlight of new mails (i used a dark blue, you can change it to whatever you want; search for 'unread' as a comment. [line #137])

Note, you have to select "Use Older Version" on GMail to use this skin, as the new version does not work with this style. (http://mail.google.com/mail/?ui=1)