tsm customize is a handy command when you want perform any sort of customizations in your Tableau Server. It can change your servername, login screen and header logo as well. All you need is a name of the server, custom logo you want to change to and a restart.
Here are the steps to do that.
Step 1) Copy your new logo to any drive on the Tableau Server
Step 2) Open command prompt as admin and login to your TSM using tsm login command.
Step 3) Update you server name using tsm customize --server-name AskLakshmi
Step 4) Upload your new logo with tsm customize --logo A:\Lakshmi\blog\post2\logo-t.png
Step 5) Apply the pending changes using tsm pending-changes apply (This will restart the Tableau server)
Observer the changes by opening the sign-in page.
Once you logged in, this is what you see.
You can use tsm customize --restore-defaults to reset all of these.