Spoiler-ish question (for those who have already seen the movie):

As far as I'm concerned they're Engineers. Look around the Human genepool...compare someone of Zulu ancestry to someone from Native American ancestry to someone from Chinese ancestry, etc, etc...

Definitely Engineers, we know at the end of Prometheus that David and Shaw are heading to the Engineer home world and that the course was programmed into the ships computer by David. The presence of their ship as well as David on that planet and the flashback of David looking down on them as he unleashes the black goo are all indicative that they reached that destination. I also found it was much clearer to see in the film opposed to the trailer that the majority if not all had the pale white tint to their skin which the Engineers in Prometheus have. Also when the black goo drops on them they break down similarly to that of the Engineer at the beginning of Prometheus.

I agree with both Blackwinter-witch and Derelict426.

I think what is causing the confusion is that they are Engineer civilians, so the general look is that of different looking individuals dressed with what could possibly be described as Engineer fashion. This is a completely different aesthetic to what is most likely the Engineer military look in Prometheus.

@Blackwinter-witch

Indeed... we also have to remember... Humans are Engineers too, we share the same DNA we came from them...

Indeed these Engineers look different, they dont have the same skin, eyes and some dont quite have the same features..

But ultimately i think they are intended to be Engineers, its just a Oversight and a Mistake made by Ridley and the Production Crew... these beings are shown for just a short time, so not much effort was made in their appearance...

We simply are not expected to notice the differences as they are only shown close for a second or so.... Ultimately these mistakes have happened before... ALIEN child Actors that made the Space Jockey about 21ft that was over done by the close ups that show the Props Size and thus 13-15ft Space Jockey.

Prometheus... 9-10 ft Engineers (12-15 in drafts) that ultimately we could all work out are just 7.5ft tall.

This is a massive massive Oversight as far as Alien Covenant. Ridley had a Attention to Detail but sometimes things slip by.. Or is there a reason so its ambiguous and so it will cause Debates and Ultimately leave the Door open to them Not being the same as the Prometheus Engineers?

Lazy, Oversight... or Genius move?

If they wanted to make these guts the LV-223 Engineers then surely Make Up like Image E with contacts like Image F would not have broke the Budget and only taken a extra 10-15 Minutes on Each Actor/Actress maybe less as we only see their Faces.

Then when making the Props for the Engineer Remains.. then have them create Larger Props that would be 8-10 ft tall... or at least 7-8...

But many are about Human size...  a Oversight?

We have NEVER Seen any Elders in the Franchise... ( if we take the deleted Scenes as just that.... deleted and not applicable).

Thus those Hall of Heads that look like the Elders, could be the Elders but they could appear more Human looking like those beings in AC rather than the Elders in Prometheus.

Thus the Prometheus Engineers, are Clones, well Genetically Engineered to be different for a different purpose... Super Soldiers if you would.

A Faction of these could Rebel, and then attempt to create its own Life hence the Sacrificial Scene.

So these Prometheus Engineers could be a Genetic Evolution of those beings on Paradise... but then the Prometheus Engineers could be the descendants to those beings all the same.

The Elders could be shown as being indeed like the Prometheus Engineers.

Its all Pretty open for Debate... and maybe its a Oversight and these are Engineers but again visual laziness has lead to them being different and we are to just overlook this.

But if this is the case, this error leaves the Door open for changes or even for nothing to be explored.. thus leaving it a Mystery that we can debate with no 100% way to confirm either way.

Finally i will add that indeed Paradise Lost was being touched up on by Ridley through out the lead up to Prometheus Sequel... right until after Alien Covenant was announced.

If we look at Paradise in context to Paradise Lost and the Bible.

*Paradise is not the place where GOD (Gods) come from.

*Paradise is not where the Angels Come from.

*Paradise is the Cradle of Human Civilization were we was Created

*Paradise is watched over and Guarded by Cherubim Angels.

This could be explored in future or at least open for debates..  The Engineer said he came from Paradise, but this could mean that his kind was one of those Tasked with Watching over Paradise before some had Fallen and then Expelled from Paradise.

Based on evidence and such above, yeah, they have to be Engineers. Most likely 'civvies' as the ones seen in PROMETHEUS do look different, but not overly-so.
That can be easily explained away as Genetic Castes or alterations due to biomechanical technology, etc..

Thanks for the answers, all. 

Has Ridley Scott ever stated in interviews (or elsewhere) that these beings aren't the engineers that David/Shaw were searching for? 

They should have just given them the black eyeballs and there'd be no question. To me that's the most curious thing that stands out, since the fleshy sacrifice engineer had black eyeballs.

if only the biomechanoid engineers had black eyeballs that'd make sense, like maybe the biomech process made their eyes black or something, but the fact that the "natural" engineer had the black eyes too, and these in the city do not, is the only thing that's weird to me. 

I will claim they are indeed engineers.

1. The juggernaut and the docking station fit like hand to glove.

2. The engineers are familiar, even please to see, the arrival of the juggernaut.

i would think they are of the same race, but the engineers from Prometheus were the buzz aldrins of the species, the brave astronauts that went out to sacrifice and did the work.

so they were happy to see the ship return, and that would also explain why the engineers from prometheus looked more fitter and robust than some of the ones in the citadel. they were supposed to be tougher than the civillians.

Just a thought I've had but this planet has more than a resemblance to the planet at the beginning of Prometheus. Could the population have been the end result of the engineer's sacrifice from that film?