Not only is the Days of Future Past X-Men storyline one of the iconic and defining stories of 80s comics, but Uncanny X-Men 141 also has one of the most iconic covers in comics. This one to be precise:
Even if you haven't ever read the comics (or even any comics) it's likely you've seen some variant on this cover by John Byrne.
Well... now it's time for a new variant, this time a mashup with Game of Thrones. Which does make a very suitable target given the death rate in the stories. I suppose technically this is a spoiler if you're not caught up with the last season of Game of Thrones, but it's actually already out of date for this season and way... way out of date for the books.
The artwork is by Adam Withers who sticks pretty closely to the layout of the original while giving it a color palette and style that more closely suits Game of Thrones.
Apparently Adam chose these three characters to appear in front of the poster because he felt they were likely the most likely to survive the story. I'm making no comment on that assumption.
Source: Comfort and Adam