you might want to check out blizo's MYthemesMCE
http://blizo.my-mce.com/phpbb2/index.php
register,then go to bug reports for the latest beta. it's very stable now,and does damn near everything you could think of to customize the mce interface. it's not for noobs tho,so please take some time to figure out what you're doing before asking silly questions-we want to keep blizo hard at work on the next build