It's been a long time coming, but Gotham has finally delivered the return of Jerome, and at this point, it seems pretty clear that the character may turn out to be the Joker. Because Jerome now has the Joker's scars, and he also seems to have changed his performance to evoke Heath Ledger's take on the character (right down to tying up captives and blowing them up). His voice is a little less boyish and excited, and a bit more gravelly, and his attitude seems to be grimmer after spending the last year dead.
Unlike Ledger's Joker, though, the audience does know why Jerome got these scars. Indian Hill worker Dwight promised that he was going to bring back Jerome, but when the time comes, he actually fails to resurrect the character in time for a big performance. This was a pretty big surprise, considering that almost every single other dead character has been brought back successfully. But instead of giving up and disappointing the cult, he attempts to make up for it by slicing off Jerome's face and putting it on top of his.
I can't imagine how terrible the inside of a face that's been dead for a year must be, but while Dwight shows up looking more like Michael Myers than the Joker, he is able to successfully spin his failure into a success for the group, at least for a moment. But once Jerome does wake up, he makes up for his absence by quickly disposing of Dwight in a televised explosion (more Dark Knight allusions aplenty, here) and using the widely broadcast message to activate his cultish worshippers, who have achieved what seems like even citywide distribution, and bid them to do evil.
With his mouth sliced into a permanent smile and dark shadows scarred around his eyes, it seems that Gotham is making its most overt reference suggesting that Jerome is the Joker to date — at this point, knowing that he's only returning for a three-episode arc seems puzzling, because he's so clearly meant to suggest a character who should be a part of this story for years.