The Last Jedi left a lot of questions open about Supreme Leader Snoke and his past, which will more than likely be answered in the years to come in some form of official canon. However, the new Last Jedi Visual Dictionary gives us some pretty interesting facts about the villain that were not told in the movie, while opening up a whole new set of questions regarding his ruling of the First Order after the decline of the Empire. One of the biggest complaints about Rian Johnson's The Last Jedi is that he did not bother to shed some light about Snoke after J.J. Abrams set the character up to be a giant mystery, so we'll take any information that we can at this point. There are major SPOILERS for The Last Jedi ahead, read on at your own risk.
A new video from Star Wars Explained took the information from The Last Jedi Visual Dictionary and did a little bit more research on what was shown in the book. One of the biggest questions about Snoke is his age and it appears that he is pretty old, maybe even Yoda old and that he was able to watch Darth Sidious' rise and then the fall of the Galactic Empire. While we still don't know how the First Order came about exactly, we do know that Sidious had a Contingency Plan in case he died prematurely that would end the Empire. Sidious died at the end of Return of the Jedi at the hands of his protégé, Darth Vader, ending the Empire, leaving time for somebody new to take the reins.
Before The Last Jedi came out, many believed that the ring on Snoke's finger had a Kyber crystal on it, but that is not the case as the Visual Dictionary points out. Instead, it is made from obsidian from underneath Darth Vader's castle, leading one to believe that either Snoke was there before Vader or possibly that they could have known each other, which does not seem likely. When looking at official Star Wars canon after the Battle of Endor, Luke Skywalker goes on a journey to find Jedi artifacts, which Snoke may have done as well as he studied the Empire before rising to command the First Order.
There are also symbols on Snoke's ring representing the Four Sages of Dwartii, which points out that Snoke was really, really old and saw Sheev Sidious in the Old Republic. Now, this points out another fan theory that suggests that Snoke is Darth Plagueis, the midi-chlorian manipulator Dark Lord Sith, who trained Darth Sidious. As with Darth Vader, they may have known each other or at least been aware of each other, but they are not the same character. Plus, Sidious murdered Plagueis. Back to the ring, again. The Four Sages of Dwartii are featured on Snoke's ring, namely Braata, Faya, Sistros, and Yanjon. The Dwartii were a group of controversial philosophers and lawgivers from the early days of the Galactic Republic, and influenced its earliest laws. Sheev Palpatine, aka, Sidious kept bronzium statues of the Four Sages (that originally belonged to Darth Plagueis) in his office during his tenure as Supreme Chancellor of the Republic. Upon becoming Galactic Emperor in the aftermath of the Clone Wars, Palpatine moved to new quarters, taking the Sistros statue with him.
When Darth Sidious became Emperor Palpatine, he took the Sistros statue with him because he admired his "political accomplishments," which may have been leaning a little bit more towards the Dark Side of the Force. The video points out that it's not very likely that Supreme Leader Snoke knew any of these characters, but instead it's implied that he studied them as they all share the same philosophy. As previously notes, Snoke more than likely picked up the artifacts along the way and adapted the beliefs to his own. You can check out the video explaining Snoke's connections to Darth Vader and Emperor Palpatine below, courtesy of Star Wars Explained YouTube channel.