On the run-up to Prometheus, there were two in-universe trailers put out that featured both Michael Fassbender's character and Guy Pearce's character.
You totally forgot Guy Pearce was in Prometheus, didn't you? Anyway, it looks like Alien: Covenant is doing the same thing as this new advertisement for Walter, Michael Fassbender's character, has just gone online.
While it doesn't tell us all that much about the character - other than his name and the fact that he now has an American accent - it does give us a sense of the tone. Everything looks a bit more darker and there's just a hint of the sinister beyond the screen. Not only that, you've also got a reference to Weyland-Yutani, the company that featured in pretty much all of the Alien franchise.
It's freaky stuff, to say the least. Take a look.