Given how little is given away of Supreme Leader Snoke in STAR WARS: THE FORCE AWAKENS, that left many to try and connect some dots. The only other "great" villain from the films that fans are familiar with would be Darth Plageus, who was supposedly killed by Sidious early on. Snoke has a pretty mangled face so it wasn't TOO much of a stretch to think that perhaps Plageus survived the assassination attempt and waited in the shadows to make his movie….except that's not the case at all.
Speaking with Entertainment Weekly, Andy Serkis confirmed that Snoke is an entirely new character to the STAR WARS canon who is also familiar with the events that have transpired in the past. He also spoke a bit about creating the character and why they went the CGI route.
Andy Serkis on Supreme Leader Snoke:
When we first started working on it, he had some rough notions of how Snoke was gonna look, but it really hadn’t been fully-formed and it almost came out of discussion and performance.
Supreme Leader Snoke is quite an enigmatic character, and strangely vulnerable at the same time as being quite powerful. Obviously he has a huge agenda. He has suffered a lot of damage. As I said, there is a strange vulnerability to him, which belies his true agenda, I suppose.
The scale of him, for instance, is one reason. He is large. He appears tall. And also just the facial design — you couldn’t have gotten there with prosthetics. It’s too extreme. Without giving too much away at this point, he has a very distinctive, idiosyncratic bone structure and facial structure. You could never have done it [in real life.]
I'm not 100% sold that they needed to go CG with Snoke, but perhaps there's more to him that we need to see. Also floating around out there is his ACTUAL height. Admittedly, I missed out on this info before seeing the film, but for those of you who were worried we may actually have a giant on our hands, fear not. Neal Scanlan, chief of creature and droid effects, gave People the scoop that Snoke is "7-foot-something tall" and "very, very thin." Not exactly the gargantuan he appears to be in FORCE AWAKENS, but he should still make for an intimidating presence. Hopefully Rian Johnson gives audiences a reason to fear Snoke come EPISODE VIII.