Below is a list of XBox Themes which are free and you can download it for XBox 360. You don’t have to use your Microsoft Xbox live points to buy them, specially the Black Ops theme, It’s awesome.
Either you can start the download of these theme from your XBox Market Place or from XBox live web page once you are signed in.
Call of Duty Black Ops : World Wide Premium Theme
Gears of War Multiplayer Map Pack 1 Theme
Call of Duty 4 : Modern Warfare : Charlie Oscar Delta Pack
Batman: Arkham Asylum – Villains Theme Pack
Free for Gold members : Download