I've seen some Gmail accounts that have either a custom image where the gmail logo would be, or, no Gmail logo at all.
Just curious how this can be achieved.
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Sign up to join this communityGoogle offers Google Apps for your domain - a way to use Gmail and other Google applications with your own domain name. You can customize some of the user interface.
Another option is to run a userscript or Greasemonkey script that changes the logo.
Lastly, there are many skins you can apply that remove or change the logo, and you can write your own skin as well.
Sound like the accounts you saw were using Google Apps for Business with custom logos
Hope this helps.