There's already an option to change your art sleeve to one of a few Spoils covers and a random tribal image.
Wouldn't it be awesome to upload your own custom art sleeves? And have them viewable by all players during a game. Strict rules as to the dimensions and file size could mitigate bandwidth issues.
I have a lovely black art sleeve with a gold Jinteki logo that would look awesome during a game, :)
Perhaps functionality for subscribers only?