Hi lovely people of STM,
Does anyone know whether using surprised face on the image creative would be a red flag for fb algo?
By surprise face i mean like those we usually see on youtube thumbnails, where they use a photo of themselves looking either shocked or surprise
Would be great to hear from anyone who has tried it before 
. Often these images are being used to claim something in the ad that will not be met eventually.
If your text and lander scream shock too this is not allowed as a whole and will be labeled as “sensational” content probably.
But using a surprised face isn’t prohibited afaik, as long as you dont do claims.
In your case - surprised face should be fine as long as your ad can't be labeled as "sensational content" and/or doesn't imply personal attributes.
Also, here are the ad policies straight from the horse's mouth:
https://www.facebook.com/policies/ads/
This page is informative and the best practice is to refer to it whenever you are creating an ad. This should keep ad rejections to a minimum (hopefully) 
thanks all!
I don’t think that the face is going to be an issue. In my experience, one of the biggest triggers is the text.
Also if you are going for a sensational type of creative with an arrow, it can be triggering for Facebook’s AI.
I really don't see why it should be a problem and why, just make sure that you use images from some sites that allow using those images for your own projects and sites, like Unsplash, for example. Avoid using faces from some celebrities or famous people and you'll be good to go.
A surprised face by itself should not be an issue. But other things, text, claim, LP, etc all can be.