Www.makingstarwars.com has reported that there will be some rather subtle changes to Kylo Ren when he appears on screen in the last Jedi.
First will be that Kylo will dawn a full black cape remminiscent of Vaders (maybe even Vaders) instead of the half cape he dawned in The Force Awakens. In addition Kylos mask will no longer be battle scorn but cleaner and newer looking.
Last but not least Kylo's face it's self will have a gruesome scar gifted to him by none other than Rey at the end of The Force Awakens.
One last tid bit outside of Kylo Ren will be that Captain Phasma will be escorted by two Executioner Storm Troopers (all in black) who carry electro pikes as weapons.
Thats all we have for now!