Customizing your Gmail Inbox identifies you as a unique individual. Some people like the old classic look like the Terminal theme, while some people prefer an earthier theme like the Turf theme. On the other hand people really don’t like any of the themes provided to them and would prefer to select their own colors and background. Gmail is now giving users the ability to not only customize their own colors for everything, but also having the ability to add your own custom background image, whether it’s from your computer or your Picasa Web Albums.
You can add custom colors to the Frame, Button Bar, Messages area, Side Frame, Side Boxes, Side Box Content and the Main Background. Each area has their own custom colors to choose from for different settings, whether its border color, background color, link color or text color. You only have the ability to add a background image to the main background, in which you can also select the alignment of the picture, and the tiling of it.
You can make your own custom theme by going under the theme tab, under your mail settings in Gmail.