Question: Why do the Predators keep skulls as trophies? At the end of the film, we see a lot of skulls hanging up in the Predators' spaceship, most of them are not human skulls and one of them looks like a dinosaur's skull, is this to make us think that the Predators came to earth millions of years ago and killed a few dinosaurs, or is it to make us think that they're the skulls of huge creatures that they killed on their own planet?
Answer: Why do some human hunters mount the heads of their kills on the walls of their house? To denote the kills that they've made, to commemorate a successful hunt. Same with the Predators. The skulls on the wall depict previous kills, one of which does indeed strongly resemble that of an Earth dinosaur. Whether this is intended to imply that the Predators have been around for so long that they hunted an actual dinosaur, or that it's supposed to be an alien species of a similar nature is unknown. Most likely the production designer simply thought it would look cool and didn't really give it any further thought.
Question: What is the significance of the flintlock pistol the Elder Predator gives Danny Glover?
Answer: It's a reference to the comic where a pirate and a predator became somewhat friendly. The gun was given to the elder predator by the pirate as a thank you gesture. The elder predator then some few hundred years later gave it to Glover as a congratulations.
Question: Right after the Jamaicans kill Ramon Vega and the predator slaughters all of them, Jerry Lambert says, "she (Ramon's girlfriend) never made it". What could she have died of? She was seen walking with Leona Cantrell and didn't seem wounded, and the predator would not have hurt her because she was unarmed. If she were wounded, she would have been checked out by paramedics right away.
Answer: Jerry means she never made it to the hospital. Keyes' goon squad intercepted the ambulance and snatched her to interrogate her about the Predator.
Question: Why did the Predator target drug dealers, and what was his interest in Danny Glover's character? I never found a connection between the two.
Answer: The predators are honour bound hunters, and as such they will only attack a target if it is capable of defending itself (i.e, if it is armed, which is why it doesn't attack the boy in the cemetary). Although the police outside were armed as well, the Predator presumably attacked the drug dealers because they were a harder target (as the police were outside he could have just sniped them from the roof tops, but he had to get relatively close inside the building) and as such, killing them gave a higher honour. The obsession with Danny Glover's character is probably because he is quite a brave and heroic person, similar to a Predator (the way he saves the other cop by risking himself etc.), so the predator may have been studying him for a while. There's also more honour in killing someone like that (as he'd be a hard target) than there is in just killing a random armed guy.
Question: Why at the end, after the Predators have appeared before Danny Glover to give him the pistol, do they camouflage themselves again? Being that they're on their own ship, and no hunt is in progress... Camouflaging themselves just seems like the special effects technicians wanted to indulge themselves one more time before the end of the movie.
Answer: It could be a precaution to keep him from attacking them once their backs are turned.
Question: At the end, what does the date and the name on the gun mean? Any significance? Other then that they have been hunting before, I wanna know who that person is, the name on the gun.
Answer: The person is not relevant. The antique gun is proof that the Predators have been visiting earth for a long time.