Just for shits and giggles, I have NO insider info whatsoever. Justice League Dark has been a great series and I've always been a huge fan of the darker side of the DC Universe, especially Swamp Thing. Del Toro recently stated that the film would focus on Constantine trying to bring this team together, but so far no one's been cast. So here's my cast wish list. I'm not just a fan of the individuals below, but I really think they'd knock the roles out of the park.
A while back I'd heard the movie may be based on the Alan Moore Swamp Thing stories that make up the A Murder of Crows trade paperback. If that's true then that leaves a few roles to fill like Dr Fate, The Phantom Stranger, and The Spectre. I don't think there's an actual script yet, but this is one I'm definitely keeping my fingers crossed for.
Anyone got any better suggestions?