The easiest way to remove this image on any 'normal' page is to override the CSS for siteImage and set it to display: none;
The downside you have here is that the All Site Content is served from the _Layouts directory which means you can't officially amend the _layout pages. Microsoft state that any amendments to these pages will break any support agreements that you have. Not sure how you can inject the css code in this case without editing the admin.Master.
Any suggestions anyone else?
www.myfatblog.co.ukMCTS: WSS 3.0
MCTS: MOSS 2007