Joomla is an open source CMS and you can modify it according to your requirements without any issues. Usually Joomla administrators prefer to replace Joomla logo with it custom logo to have their own branding.If you don’t want to see the Joomla logo which appears in the backend and replace Joomla logo with your own logo then you have to follow few steps to achieve it.
In short you can Replace Joomla Logo easily with your own logo using the above steps. But keep in mind that the size of custom image which you upload must be of same size or proportional to that of the Joomla default logo. We would also recommend you to use a png image instead of jpg or gif.