In addition to our relentless browsing stemming from our terrible internet addiction, we're admittedly Gmail-holics. And big ones too. Personally, I use Thunderbird and Gmail's IMAP service to keep all of my e-mail addresses synced to one place, but I know a lot of people who enjoy not having to install extra programs when they could just log online to check their mail. I've tended to keep away from the online setup mainly because I was never fond of the original look Gmail had going on...
However, starting today, that issue's long gone, courtesy of Google. Say no more to all that white space... you can now have ninjas, MS-DOS green against black, and a slew of new skins to keep you busy for the next few days picking out which one you like best.
To customize your inbox, go to the Themes tab under Settings. You should be able to find a theme to your liking from there.
Google will be rolling out themes to everyone over the next couple of days, so if you don't see them yet, check back soon.