How might games benefit from procedural pictures?
Once obvious answer is settings. I don't know what they're called, but film directors once commonly used landscape paintings to create grand scenes (like the backgrounds of theater plays) without having to relocate the whole production team. Film director John Ford used such backgrounds in all of his movies with John Wayne. In the film Darby O'Gill and The Little People, Disney used a combination of such paintings and mirrors to create fantastic illusions of scale. You don't see this technique in films so much since the advent of computer technology. But it can be seen in many games, like Hellgate: London and Assassin's Creed.
Procedural pictures might be useful wherever you would normally place a background picture. I don't know how much time and thought it takes to make a procedural picture (ask axcho), so I can only guess that the rewards might sometimes outweigh the expense. But such basic procedural generation is light on processing, and the possibility of including a dynamic, animated background without burdening other systems is certainly attractive.
As backgrounds, procedural pictures would be particularly useful in areas that players will return to often: log-in screens, banks or vendor shops, inventory screens, etc.
I'll try to think of less obvious possibilities later. Any ideas?