Let's play the "speculate on what the new creatures do" game!

[Ballzanya]

Well, I figured it would be interesting to hear what people had to say as to what exactly these new parasitic creatures do to their hosts. Do they also have acid blood? etc.

The whole "hammerpede" in the soundtrack got me thinking. That cobra headed thing doesn't have multiple legs. Also from that beer commercial, it became clear that it wasn't the same creature that came out of milburn's mouth. If my speculation is correct, the hammerpede is what comes out of his mouth and possibly grows larger.
  Then there's the squid thing shaw is impregnated with and the mutations holloway and fifeld go through.  Also there's that blue tentacle we see hit the door in the imax trailer. Don't know what to make of that.
Also, the murals of that xeno looking entity have got to be related in some way to the movie.

[ChrisPachi]

I hope that it is a primal beast like the xenos that we know; It gets into a host and either eats it from the inside or lays eggs for more creatures. The one that jumps out of the mouth looks pretty small, whereas the one that...

Spoiler

..gets in Milburn's mouth...

[close]

...is pretty big.

[AsapJockey]

SPACE TAPIRS RAPE EVERYONE IN FREE FOR ALL ORGY SCENE WHICH MAKES ORIGINAL ALIEN

[Ballzanya]

I hope that it is a primal beast like the xenos that we know; It gets into a host and either eats it from the inside or lays eggs for more creatures. The one that jumps out of the mouth looks pretty small, whereas the one that...

Spoiler

..gets in Milburn's mouth...

[close]

...is pretty big.

yeah but so does a chestburster compared to a regular alien. If these species parallel that parasitic life cycle in some ways, we'll be getting a creature that is at least bigger than this thing.
  Now if would be interesting if this thing bites fifeld or holoway and infects them with some kind of poison venom.

[RoaryUK]

What I think is this Hammerpede will go from one person to another, infecting the crew with some virus that drives them crazy, possibly for some other purpose rather than just killing anyone. I'm also of the opinon it's these things the Jockey's unintentionally created that caused them to leave in the first place. Holloway I think will somehow come in direct contact with the black goo, either by accident during an expidition or possibly through David who it probably doesn't affect, but either way he won't be aware of it. This stuff seems like it could be full of tiny worms, I think will go on to transform Holloway into this human version of the Jockey we've seen so much of, but before it takes hold he has sex with Shaw causing her to become pregnant very quickly, the infection going into her baby not her which might be the key to a few things. The creature eventually removed from Shaw will become known as the Proto Face-hugger, which I think might actually change into something else by shedding it's skin, taking us into that last 8 minutes we've heard so much about. These things seem to be the most obvious I think, what happens after that is anyones guess.... 

[Salt The Fries]

Now if would be interesting if this thing bites fifeld or holoway and infects them with some kind of poison venom.

So poison or venom? You can't have both at the same time. Venom is injected, poison is ingested or inhaled.