Board Thread:Support Requests - Getting Technical/@comment-5068292-20150119062619/@comment-6969786-20150119121255

You change the logo image ( the Runescape Logo on your example ) by using the Theme Designer

Special:ThemeDesigner

With the Theme Designer you can change the Logo, Set the Background Image and change the Favicon among other theme related things.

However I believe you must be a Admin to access the Theme Designer, which I asume you are.