Microsoft has added a new feature to the Xbox interface called Event Themed Backgrounds. It allows thematic images to be placed on the console's home screen and, apparently, is used to promote Call of Duty: Modern Warfare 4.
Unlike dynamic backgrounds, the new feature retains the selected image even when switching between different games. Thus, the promotional background remains on the home screen regardless of which project the user opens or selects in the menu.
The innovation caused dissatisfaction among some of the Xbox community, as themed backgrounds are enabled by default.
The feature can be disabled manually. To do this, go to Settings → General → Personalization → My backgrounds and change the corresponding parameter.