If you don’t know how to do gmail background change then you must follow the steps:-
1. The first step is to open Gmail and then log in to your account.
2. Now click on the Settings icon which is present on the top right corner of the screen.
3. Then scroll down in the quick settings and find Theme and click on View All option.
4. Now choose a theme of your choice and click on the Save option.
5. You can also click on the More images option if nothing suits your taste.