What are some current user acquisition creative trends?

This is also a good portal from FB to see what kinds of ads other apps and developers are using for promotion. If you look at apps in your specific genre, you can probably form some cool insights on trends. 

https://www.facebook.com/ads/library/

Creative trends are entertaining to watch because they showcase just how quick mobile advertisers are to follow what they see their competitors doing.

I think the canonical example here actually isn't the current weird Homescapes / Matchington Mansion ads that totally misrepresent gameplay: those are egregious but they are actually pre-dated by ads that FunPlus was running for King of Avalon that showcased 3D action gameplay that looks nothing like the game experience of King of Avalon:

https://www.youtube.com/watch?v=ALwCuayoO5Y

https://www.youtube.com/watch?v=07iFZ_4iwqo

In any case, you can watch these fast-follow trends evolve in real time just by scanning Instagram. I am working on a project in the Health and Fitness space right now and there are a few noteworthy trends that every advertiser seems to have picked up on:

1) Abs with accompanying exercises:

2) Some sort of exercise calendar:

You'll start to see this very unique / iconic imagery for one app and then suddenly every app in the space is using some variant of it within a week or so.