The ALIEN movies are all very focused on specific dramatic situations, mainly the confrontations with the xenomorphs. That's fine and a part of the genre, horror in space. Still, we sometimes also get glimpses from a larger dystopian world. There are a lot that could be expanded into plot details or other useful RPG stuff. What do you think would be cool to know more about? Here are a few things that I thought of:
1. The Lacerta Plague. This unknown epidemic was just briefly mentioned by Call in the fourth movie, so it might be something that happened quite late in the ALIEN time frame (or maybe not!). It sounds like a disaster that killed many. Where, when and how? Is Lacerta a place, a planet, a company, a plant, or a person? Was it a lab created virus weapon or something strange from a distant planet? Is it still around?
2. The autons and their rebellion. Call was an auton, a "second generation" synthetic created in 24th century. They were so well programmed that they revolted against their unethical, human masters. There is a history in all this. How did the synthetic industry change and why? Who created and produced the autons (apart from Weyland)? Who made profits from this production? What was the real agenda?
3. What is the real legacy of Peter Weyland? He is obviously a central figure in this setting. He created Weyland Industries and its´s project Building Better Worlds. How has this project evolved? What did Weyland really know? What is in his archive? Where is it? We know he died after being killed by an Engineer, but that was perhaps not the real end of his existence. I would imagine his DNA was preserved and perhaps cloned. Who took care of this? What happened through the years? If there are (living?) remains or clones, who and where are they and what are they doing? Maybe there are several generations of them, hating and/or loving each other. There might also be an AI copy of Weyland, since he was open to that kind of existence too. There might even be some kind of secret cult around his legacy within The Corporation. I imagine a bizarre Lunar mausoleum with lots of strange and extremely valuable stuff.
4. What was the long term scientific outcome of the xenomorphs? Just from very small samples a lot of strange things can be done in a lab. For example, there might be extreme drugs or maybe even knew materials. Who has this stuff? Where is it kept? What can be done with it? Is it dangerous? Can it be bought or stolen?
5. Walmart in space. In the early 24th century The Weyland Yutani Industries was bought by Walmart. It´s a funny detail (introduced by the French director Jean-Pierre Jeunet, I guess as an ironic gesture towards the American franchise), but it also evokes questions. When and how did Walmart become a power in this context? Did they produce spaceships, synthetics or something else?