The project was first referred to as Heaven Sent, but Guillermo Del Toro says the working title is now Dark Universe. It's to be a DC comics-derived film that steers away from Kansas farmsteads or fetishwear vigilantism in favour of the monstrous and supernatural.
Better still Del Toro says that writing is underway now. He's working on the outline himself and has the "perfect" writer, somebody who is "very, very good" and while he won't say who, Del Toro says this writer has accepted the gig.
The following video from IGN features Del Toro talking about the line-up of characters. Swamp Thing is "a rockstar" to him, Etrigan the Demon is "amazing." He also notes that wants to do "the Constantine of the comics" and that The Spectre, Deadman and Zatana Zatara will all also appear. Other characters are kept secret so that we can't guess the plot - which seems to be a clue in and of itself.
Also note that Del Toro clarifies Warner Bros. are looking to make a "cohesive" movie universe. He seems to be implying that their existing Superman and Batman films are the "foundation" of this. What does that mean in relation to the John Blake/Joseph Gordon Levitt rumours? Are they really not going to reboot Batman? Have they really set Man of Steel in the same continuity as The Dark Knight?