For those of you who think that Gmail’s interface looks dull, here comes Gmail themes. With this new feature, you can customize your Gmail to your likes.
Gmail now gives you the option of selecting from its collection of themes such as New Blue, Steel, Green Sky, Shiny, Beach, Mountains and many more.

To enable this feature, go to ‘settings’, and choose ‘themes’ from the tabbed menu. Then just click on the theme you desire ….as simple as that.
There are many more functionalities of Gmail that are in beta stage like mouse gestures and pictures in chat, and if you like to test them out, go to ‘Labs’ from the ‘settings’ page.