MSW have some juicy tidbits up about a new planet to be featured in The Last Jedi. Here's a quick snippet:
Of those worlds, there’s one we haven’t heard discussed much. We heard about a new planet from Star Wars: Episode VIII last year during filming that appears to be really important to the story of the film, and that is the “Mars with snow on it” planet. The way I heard the set described, it was like Mars, a red ground, but covered with a light layer of snow, especially on the banks and rim of a hallway-sized trench. So imagine “Mars if it lightly snowed” is the mantra for this place. We heard the interiors were not unlike Starkiller Base in the sense that you can see the Death Star-style tech and architecture blending in with the rocks and natural environment.
The planet is likely a First Order-controlled world and it is hard to not speculate that this is where Hux, Phasma, and Kylo Ren meet up with Supreme Leader Snoke after their failure in Star Wars: The Force Awakens.