Supreme Leader Snoke has come and gone, with nary a clue to his origins. Well, except for one…which, honestly, kind of lends some credence to all those "Snoke is Darth Plagueis" theories. For those who don't know, Darth Plagueis was the master of Darth Sidious/Emperor Palpatine, who eventually killed Plagueis during his rise to power.
You could only see it clearly in two or three shots, but Snoke was wearing a pretty weird-looking ring—located on his left hand, it had a gold base with a black stone rising out of it. According to The Last Jedi: The Visual Dictionary, the gold section is inscribed with "glyphs of the Dwartii." Dwartii is a planet that was home to the Sages of Dwartii, four mysterious philosophers who were apparently revered by the Sith, judging by the statues of them in Palpatine's office in Attack of the Clones. The novel Darth Plagueis also suggests that one of the statues belonged to Plagueis before Sidious killed him.
It isn't exactly a strong connection to Snoke, but the markings on Snoke's ring are literally one of the handful of times Dwartii have shown up in Star Wars. While it's doubtful that Snoke really is Darth Plagueis, the ring suggests there may still be some connection between the two.