With Photoshop i used a technique called 'Invert', which is basically using a negative setting. I would like to use this effective for a still shot within the trailer, i think this would be effective as it would emphasis the eeriness of the film.
I changed the hue/saturation and contrasting to give an obvious knowledge of what might happen, the red representing the spilling of the blood from the victims. I like the hidden meaning from this picture, the blood red over the grass suggests that death lingers there permenantly.

