Gmail's web interface can now be customized even further, as Google has added hundreds of new themes for users to pick from, along with some new emoji as well. There will be tons of new images to select from as the background, some of them captured by Googlers themselves, and once you find the right one you can use Google's editing tools to make it look even better with your messages. The editing tools include blur, vignette, and text background, all of which allow you to make the image look better with your inbox.
In addition, Google has added an 'emoji for just about every occasion', so now you don't have to hunt down the right words to express how you feel. These updates are rolling out over the course of the next few days, so if you don't see the changes just yet be sure to check back in the next day or two.
Source: Gmail Blog