In many awaiting the arrival of a feature like this for several years now and now, finally, after providing the ability to set the wallpaper, Google has decided to make it available in Gmail and a new special section through which to create custom themes for your inbox.
Announcing the new feature is a special article published on the official Gmail blog which also discusses the various ways by which you can use the new Custom Themes section in conjunction with a special video demonstration attached to the end of this post.
The rollout will be completed in the next few hours but are still many users who have had the opportunity to test the features of the new section called, precisely, customized Themes.
To immediately begin to customize the background of your inbox will just go to Gmail's Themes section, then select, in the entry personalizati Themes, Light or Dark option depending on your needs and personal taste (the difference is the color of the button labels and the background of the message) and then select the image to use.
The images can be obtained directly from Picasa, or, again, you can pick up those shared by their Google account, select images directly from your smartphone (in this case is a necessary prerequisite and necessary to have installed please on mobile devices Google + Android or iPhone) from your computer, or even entering the url reference.
Then users need only click the Select button to apply the custom theme in Gmail just created.