I believe the First Order, who are the remnants of the Empire, are now controlled by of the Order of Revan. The Order of Revan or Cult of Revan were a secret society who followed Revan, a fallen Jedi, who used both the power of the Darkside and the Light. Sound familiar? Here's a quote; "The secret society known as the Order of Revan is known only to its members and a few inquisitive outsiders. The society is believed to be several hundred strong, ranging from powerful and influential Sith Lords to military officers and alien slaves–low status is no barrier to entry, but personal power and fervor are everything. Some so-called Revanites devote their lives to the cult’s teachings and exist outside of mainstream Imperial society; others study and meet in secret while maintaining ordinary lives. The Order of Revan takes its name from an ancient Sith Lord–a fallen Jedi who used both the dark side and the light side of the Force during his lifetime. Revan drew strength from passion, as well as tranquility; took allies who were human and alien, weak and strong. Revanites seek to emulate Revan’s ways, seeing him as the greatest of all teachers." -In-Game Codex. "Snoke was very old, having a vast knowledge of the past and of the Force. He displayed tendencies unusual for practitioners of the dark side, displaying an interest in Kylo Ren due to his embodiment of a balance between both the light and dark sides of the Force, as opposed to only one aspect." -Wookiepedia. So, Snoke is obviously a Revanite. Luke's Jedi Academy was on Yavin IV and,coincidentally, the remnants of the Order of Reven, after they were exposed and hunted down by the Imperials and the Republic, retreated to the moon Yavin IV. Snoke was most likely on Yavin IV all along and seduced Kylo Ren secretly, meeting him while Kylo Ren was exploring the planet. Of course this is just conjecture, but following this tract of logic, it would narrow down who Snoke could be to the few members of the Order of Revan who retreated to Yavin IV. Snoke could even be Revan himself, although he is supposed to be dead, the movie has already deviated from the lore in respect to the destruction of the Jedi Academy, so reviving Revan would not be a big surprise. Revan's ultimate goal was the destruction of both the Republic and the Imperials. He wanted to unify both under his rule and teachings. The war and eventual defeat of the Empire left both sides weakened and would provided the perfect opportunity for Revan to make his move. Revan also had implants in his left cheek and forehead above his left eye, which would account for the Snoke's scarred appearance, if he tore them out or they were destroyed in battle. (Sith lightning attack) And finally, the mask that Kylo Ren is wearing is almost identical to the "Mask of Revan".