Gmail recently added the ability for users to customize their inbox by applying themes. The theme library contains everything from a terminal window style to graffiti.
Googe just released two new styles for Gmail, and a way to make your own. The first one, "High Score", reminds me of Super Mario Bros. It's got an old-school video game feel, which I'm sure most of us can relate to. Turf is another new one -- and it's actually quite polished. It's got a grassy feel, with nice transparencies and easy to read text.
In addition to these two new themes, Google has also given us a way to create our own themes -- basically mixing and matching colors for all the different elements you can find in your Gmail.