The only browser which is still in beta and accepted by millions of users is Google Chrome, only available for windows where as Mac and Linux version is still under development. Even though Google Chrome lacks many features like official themes, plugins, extensions and add-ons but there are several unofficial ways to get them like you can have Google Chrome theme.
Before Google Chrome comes up with official document for developing themes, a tool to develop Google Chrome themes is already available. Google Chrome Theme Creator is small utility which lets you to create your own Google Chrome themes.
Screenshot of Chromium Theme Creator
Check out Google Chrome Theme Manager XChrome