It seems to be based on X-Men #141's cover from [***Days of Future Past***][1].

[![X-Men #141 cover][2]][2]

Characters in *that* poster.

Top Left - Bottom Right

 1. Cyclops
 2. Colossus
 3. Storm
 4. Nightcrawler
 5. Angel
 6. Iceman
 7. Beast
 8. Sprite
 9. Magneto (Gambit in '97 poster?)
 10. Quicksilver
 11. Jean Grey (Scarlet Witch in '97 poster?)
 12. Wolverine
 13. Forge? (Professor X in '97 poster?)
 14. Polaris
 15. Havoc
 16. Banshee


  [1]: https://en.wikipedia.org/wiki/Days_of_Future_Past
  [2]: https://i.sstatic.net/mO13C.jpg