It's worth saying that you will need to redo your changes each time the Meeting application is updated ie with a fix pack or similar so because of this I have stayed clear of such customisations. I know Robert Farstad did some customisations although I don't know what version it was on and he hasn't shared it with me.
https://kbild.ch/2011/10/customizing-the-sametime-meeting-center-ui/
https://twitter.com/robertfarstad?lang=en