Gmelius is a browser extension available for Google Chrome, Mozilla Firefox and Opera Browser.
The basic idea is to modify the Gmail user interface to make it better for you.
Here are some of the features it offers:
Remove all the ads
Make Gmail header collapsible
Removes the People Widget
Colorize the buttons and have both text and icons in them
Add row highlight color
Remove custom fonts and colors from mails
Add attachment icons to mails in the inbox
Gmail logo can be made clickable
Scroll to the top by clicking the Google Navigation Bar
Regain screen space by optimizing the layout