If you want to wish anyone Merry Christmas but still remind them how close we are to the world coming to an end, you can use the new Fallout Shelter (Free) seasonal stickers added today with update 1.9. There are now new Holiday Stickers, which are admittedly quite charming though with an undertone of dread if the recipient knows what the game is all about. Update 1.9 has added more than just stickers. We are also getting new quests that will have your cabin-crazy dwellers traveling to some caves. And knowing the game, what could go wrong in a bunch of caves, right?
In addition to the cave-dwelling quests, the game has added Faction Theme Quests as well as Daily and Limited Time Holiday Quests. In other words, more reasons for you to visit your vault and all your guinea pigs (I mean dwellers) more often. The update is out, so go check out those caves.