Film stills that could be useful for trailer

I believe using mirrors within my trailer would be effective as you can use them in many ways.
You can use them to make the audience see something the character cannot, which puts the audience at an advantage over the character. For example, the camera could be looking at a mirror in which you can see the characters reflection in, and something/someone scary could walk behind the character. The audience can see it, but the character cannot. This is effective as it creates fear as the camera is not aimed at the “monster”, but instead its reflection. Therefore, a way to take this shot further would be to have the character notice the reflection of something behind them, turn around to see what’s behind them, whilst the camera aims at the character instead of the mirror, and there to be nothing there.