This JC thread talks about the new 3D set picture[$] on the Official Site tonight.

The picture is of a conference room on the final planet of the film. It is made of metal and looks pretty rough. The leaders of the Confederacy will meet here to figure out their next plan of attack and the events at the end of the film unfold. To that end, Nick Gillard inspects the environment.

TFN fan JZ thinks it might play out something like this in his speculation (possible spoilers - highlight to read):

The Separatists leaders are on Mustafar, sitting around the table in the middle of a conversation awaiting Palpatine's emissary - suddenly the door opens, startling all of them. Anakin strides in with his head down, the door closes behind him and he slowly looks up with an evil grin on his face. One of the leaders attempts to get up from the table and run, but Anakin is too quick for him and uses the Force to throw him against the wall, knocking over his chair, and choking him to death. The Sep. falls to the floor and the rest of the leaders turn back to look at Anakin.

His lightsaber ignites and we cut to Obi-Wan and Padme's journey to Mustafar. They arrive on-planet and begin the search for him. We cut back to Anakin in the conference room, corpses of the Sep. leaders littering the floor, with Anakin following a terrified Nute Gunray around the table. He suddenly moves in for the kill and severs Gunray's head. His limp body falls to the floor as Anakin continues to grin evilly.

Padme rushes in and Anakin spins around, his emotions taking a new turn as he sees his pregnant wife, waves of guilt and shock riding over his face, and he becomes distressed that she is seeing first-hand his handiwork and also that she's on this very unstable planet. She runs up to him and tries to talk some sense into him.

Suddenly Obi-Wan bursts in, Anakin reacts with his heart rather than head, and accuses Padme of betraying him. He begins to Force-choke her, causing Obi-Wan to ignite his own saber and come running towards Anakin, who throws Padme aside where she hits her head hard and falls to the ground. Master and apprentice begin their epic duel.

Man, that would be sweet!