Is Andy Serkis' Supreme Leader Snoke from "Star Wars: The Force Awakens" actually Darth Vader? In a word: no. But even we have to admit the spooky resemblance between the two.
Ever since "The Force Awakens" hit theaters, fans have been theorizing on who Supreme Leader Snoke is and what his origins are. For all of its many, many positives, "The Force Awakens" can be knocked slightly for not providing much background information on many of its new characters. Perhaps that is why fans are latching on to this Vader theory.
However, it doesn't make much sense. When last we saw Darth Vader at the conclusion of "Return of the Jedi," he was as close to death as you can get while still being alive. We then see Anakin Skywalker as a Force ghost alongside similarly deceased Yoda and Obi-Wan Kenobi. That's pretty convincing in and of itself. But it also doesn't make sense that Vader would return to evil as Snoke after redeeming himself and finally bringing balance to the Force by killing the Emperor. That turn would lose all of its importance if he immediately went back to his former evil ways.
So, yes, the picture is definitely curious. But Snoke's resemblance was likely intended to evoke familiar feelings in "Star Wars" fans as opposed to being a twist of this magnitude.