I'd like to take advantage of all my solo rides through the subway system by using a new "graffiti artist" upgrade card. With this card you gain the ability to draw graffiti on the subway. This graffiti could be captured with a camera but would disappear once you leave the train (those efficient maintenance bots are a marvel). Don't go crazy with colors like in vanity, just give us a random primary or secondary color that works with the subway train palette.