Explanation of where the assets in these folders are used
ICON0.PNG - Icon used in various scenarios depending on if it's used for a save or a game. This includes when:
> The game/save isn't selected in the XMB 
> There is no ICON1.PMF present (XMB only)
> The "Group Content" mode is enabled in the XMB game selection menu
> The game is on a save management screen with UI elements shared with the XMB (note the font)
ICON1.PMF - Seen when the game/save is selected in the XMB (NOT IN-GAME)
PIC1.PNG - Seen as a background when the game/save is selected in the XMB
SND0.AT3 - Plays when the game/save is selected in the XMB (NOT IN-GAME)
EMPTY.PNG - Used as an icon for empty saves when selecting a save to write to.