The shots of LV-1201 seen from space are actually shots of Mars.
The Marines' ship, the Verloc, is named after a character in a Joseph Conrad book. The ships form the first two Alien movies (Nostromo, Narcissus, and Sulaco) also got their names from Joseph Conrad books.
During the first Marine mission, a series of notes can be found written by a security guard named Joss Blaney, detailing the events between the Incident (when the Primary Operations Complex was overrun by Aliens due to the actions of the player) and the arrival of the Marines six weeks later. As the notes reveal, after the death of the POC Commander (the character appearing in cutscenes of the second and third Alien levels, identified as Liam Hadden) Blaney led a ragtag group of guards and convicts (led by a man named Xavier) struggling to survive in the Alien-infested POC, and gradually realized there were Predators lurking about as well. At one point, the Marine player finds a corpse identified as Blaney the dogtags laying nearby.
This game features the return of the quadrupedal red Alien from Alien 3 (1992). They are named 'Runners', a name which has stuck in Alien fandom. In Alien 3, the creature emerged from a dog (or ox, as depicted in the Assembly Cut), resulting in a quadrupedal gait due to the Aliens' ability to adopt genetic characteristics of their hosts. The presence of dogs and cats on the LV-1201 research base is mentioned, and the 2002 Primal Hunt expansion pack reveals quadrupedal native fauna that could have spawned Runners, as well. In multiplayer, Runners are spawned from 'Corporates' (Iron Bears) due to there being no playable quadrupedal animals in the game. Marines spawn regular Aliens, Predators spawn Predaliens.
Notes found in the Forward Observation Pods in the middle Marine and Predator levels detail a lot of intrigue amongst the scientists. For instance, a Dr. Betheny Clements is impregnated by a Facehugger mere days after a confict with her superiors, suggesting foul play. Also, various characters voice their suspicion of General Rykov and his Iron Bears.