I once saw a horror movie that had scary, weird, subtle things in the foreground. For example, the main one I remember was early in the movie, when it was still keeping the viewer in suspense about whether anything supernatural was happening; in that scene the camera panned across an area and the silhouette of a ghost was right up front, but easy to miss. It's the only movie I can recall doing that; I was watching the movie with my then-girlfriend and she didn't even see it until I rewound to show her.

I can't remember the name of the movie, I'll have to ask my now-wife, but it was quite good.

edit: Actually managed to remember on my own. It was The Awakening.