Currently, it would appear Scott is adopting a similar strategy for this movie as he did in 1978/79. No one was allowed on set. No one knew what the creature looked like. We saw a slow trickle of content in the form of magazine articles and photos. Images of the Alien were not released prior to the release of the movie (not to my knowledge, anyway.).
We did see images of the Nostromo crew and of the ship itself, both interiors and exteriors. We saw images of the derelict and the Space Jockey. These were gradually released over time in magazine articles and reviews. Specialist periodicals such as 'Starlog', 'Fantastic Films' and 'Starburst' were the main source of such content.
The amount of secrecy hasn't changed but the real achievement here is how Scott has managed to keep leaks down to almost nothing in an age where the whole World knows what's going on in an instant something gets released. That level of secrecy is an achievement on its own.
More or less, though, 'ALIEN: Covenant' is mimicking the promotional strategy of the first movie. We'll start seeing images of the crew very soon. Maybe a few spacecraft interiors and exteriors along with them. The Creatures(s) will come later. That's my theory, anyway.
-Windebieste.