You can customize your Gmail under Settings > Themes
Gmail’s Ninja Theme
Google has just rolled out new themes for Gmail and it’s uber awesome.
To customize your Gmail inbox, go to the Themes tab under Settings. 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.
Now, you can compose mail or read older mails while you’re in the subway or just about anywhere while you’re offline. You can even switch to your other Gmail accounts or E-mail accounts using Google Apps. All you need is to download Gmail for mobile 2.0.
Just go to m.google.com/mail in your mobile browser to download the new Gmail for mobile for your phone.