Windows 7 Media center have multiple switches for customization.

Here is a list bellow.

/nostartupanimation stops the startup sound and Windows Media Center logo "pebble" going off into the distance
/noshutdownui removes the "shutdown" item from the tasks menu
/mediamode starts in media only mode (no close/minimize/maximize options in top right corner)
/widescreen start in widescreen mode, even on 4:3 display (windowed only)
/nochrome display windowed mode Media Center but without the window chrome
/playallmusic plays all your music instantly
/playfavslideshow plays your favorite slideshows only
/playfavslideshowwithmusic plays your favorite slideshow with music
/playslideshow plays all slideshows
/playslideshowwithmusic plays all slideshows with music
/screensaver starts the Media Center screensaver
/configuress  starts Media Center at the "configure screensaver" screen
   

Examples: %windir%ehomeehshell.exe "/mcesuperbar://tv?live=true"   – That will start Media Center in LiveTV mode

Yo can create custom shortcut by doing the following : Start > All Programs > Windows Media Center, and right click on it. Select properties. Under "target" you will see "%windir%ehomeehshell.exe".
Media Center Properties

Simply add the switches you wish Media Center to start with and hit OK.

For example, if your shortcut looked like the following: %windir%EhomeEhshell.exe /nostartupanimation /noshutdownui /mediamode

Media Center Properties /nostartupanimation /noshutdownui /mediamode