A lot of people have been speculating who Snoke could be since he was revealed to us. Some people think it could be Vader. Others think it could be the Emperor's master. Or is he something completely different?
To start I feel the whole Snoke being the Emperor's master could work and I could see it. Snoke could have been playing puppet master all along without us knowing it and it is definitely a cool thing to think about. Snoke could of started the Sith Order and recruited Palpatine as a padawan from a young age. Then he could have trained Palpatine to become Darth Sidious infiltrate the Jedi Order and Republic Senate as a way to stay one step ahead of the Republic. Then he could of started the Sith Uprising and had something to do with Anakin killing most of the Jedi Order. Then he could of created the Empire as a means to control the Galaxy. Then he could of established the First Order to finish what Palpatine started. Although it is a great theory I'm not sure how likely this would be, but I would love it to be true.
Now one being theory is Snoke is actually Darth Vader. This would be a huge plot twist if it was true, but it seems absurd. Vader dies on the Second Death Star when he prevents the Emperor from killing Luke and he kills the Emperor. But the electricity runs through his suit and he dies. Then Luke burns his body and helmet at his funeral. Then Vader comes back as a force ghost of Anakin Skywalker at the end of Episode VI. I feel theory is absurd and it's only based on looking similar. It reminds me of the whole Jason Todd is Joker theory.
Lastly I feel Snoke is actual a force ghost that died long ago even before the Clone Wars to pull strings from the afterlife. I feel he was a Jedi as powerful if not more powerful than Master Yoda. He then was betrayed by the Jedis and died. Ever since then he's been trying to eradicate the Jedi.