Joker the Artist
Here's an aspect to the Joker's character we haven't seen in a while: His love for art. The Jokers we've seen in the movies so far (I'm referring to Heath Ledger and Jared Leto) seem more concerned with making some kind "statement." They're basically terrorists trying to force their doctrine on other people. In the Joker's case, it's a very nihilistic, anarchist doctrine, but it's a doctrine all the same. Everything burns.
Now, take another look at Jack Nicholson's Joker in this scene. He doesn't care so much about making a "statement" as getting away with petty vandalism on some of Gotham's most expensive paintings, and having fun while he's doing it. With the other Jokers, business came before pleasure. They're twisted souls only pretending to be happy. With Nicholson's Joker, it's all ABOUT pleasure. He's having a blast and loving every minute of it.
Next, watch the Joker and Vicki's conversation:
The Joker describes himself as "the world's first fully-functioning homicidal artist." He might mangle art, but he doesn't burn it. In that way, he's less nihilistic than Ledger or Leto's Jokers. He's still a monster and a killer, of course, but he doesn't care so much about burning down the world, as leaving his own impression on it, like any striving artist would. He makes people into his own "sketches" and "paintings."
I don't know about you, but I'd love Telltale to bring back this angle to the character with Anthony Ingruber's incarnation. It would also allow Telltale to dig a little into the theme of art vs. commerce whenever the Joker interacts with Bruce Wayne. Maybe that's the "favor" Joker is looking to get from Bruce; like any starving artist, he just wants to secure some funding for his special little projects.