I am using this for long time on multiple skins - mimic, aeon, bello. I have different backgrounds when I select each item in main menu - movies, tv series, etc. Backgrounds are showed randomly, as slideshow and they depends from my library. So only fanart of movies I have currently on storage for playback is displayed.
To achieve this, the skin itself mus support to set background for each main menu item. Like you can set widgets for those items. Its realized mostly through plugin like skin.helper.backgrounds or skin itself does it. If supported, you can select from multiple background choices like random tv series fanart, random movie fanart, etc. I can provide screens to better understand.