If you don't like the Windows Live logo that's staying in the top right of your Messenger 6 window, just go to Microsoft Messenger app in the Finder. Control-click on it and select Show Package Contents from the pop-up menu. Then navigate into Contents -> Resources and remove (or rename) the ContactListMSNLogo.png file. That will put a white rectangle in that spot instead. Not perfect cosmetically, but better much better than the original look!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060928091326369