Between now and December 15 Star Wars fans are going to put forth theories about what's going to happen in the Star Wars: The Last Jedi, and throughout that same period Mark Hamill is going to mess with them. One of the more recent theories that has been proposed, has been the idea that Luke Skywalker could go bad in the new film. This theory is based on the fact that the new North American poster puts Luke at the top and in the back of all other characters, a position held by the villain in many previous Star Wars theatrical posters. However, Hamill is now messing with the theory by presenting another Last Jedi poster for another region, that would seem to have a different villain.
As it turns out, a similar poster being released in Asia doesn't put Luke Skywalker in the "bad guy" position, but instead, it has Rey. Mark Hamill sent the poster out via Twitter with a fantastic conspiracy theory hashtag, likening the "Luke is evil" theory to the classic urban legend that Paul McCartney died and was replaced as a member of the Beatles in the 1960s.
To be fair, the "Rey is evil" theory at least has some more support to go with it. The most recent trailer for Star Wars: The Last Jedi, is certainly designed in such a way to make us think that Rey might turn to the Dark Side. While it's possible that all that is intentional misdirection, that idea combined with this poster would feel like they were designed to reinforce the same idea, assuming you believe the whole, the bad guy is always at the top of the poster, thing.
It is absolutely true that there are many posters for the various episodes in the Star Wars saga that include Darth Vader or the Emperor in that top position. The fact that these posters just crazy with character portraits have become a staple of the marketing, it's no surprise that some sort of standard layout has come to the forefront, though that's almost certainly unintentional. Due to the fact that Lucasfilm has been keeping spoiler information so close, it's unlikely that whoever designed the poster even knows if anybody, Luke or Rey, is actually going to go over to the Dark Side.
The truth is, that China has never had the connection to Star Wars that we've had in the west. This means that making Luke Skywalker the major face on the poster simply wouldn't make sense there. Anybody in China who is looking forward to the follow up to Star Wars: The Force Awakens is probably most interested in Rey, so she's given the focus on this poster. It's marketing, not a spoiler. Tickets for Star Wars: The Last Jedi are now available for pre-order.