The icons remain for all apps that are installed. If want to remove any of them, you need to uninstall the corresponding app. The only other option is to install Panda Home. It has an option to hide the icons from the app tray. There may be other apps that allow you to do this, but the only one I've tried is Panda Home.
As far as I know you can't remove them...I personally haven't tried, but I've read in a previous post that we weren't able too...Im sorry I cant help you more, hopefully someone else can give you something better to go on...Sorry