Conventions of a thriller poster (Silence of the Lambs)

The progression from light to dark (left to right) of shadowing represents the fact that she was something pure, slowly progressing into the darkest case she has to deal with

The main focus of the poster infers that the main focus of the film is her, and therefore suggest the surrounding features in the poster are obstacles she has to overcome or solve.

The butterfly symbolizes progression and transformation into a new being. However the skull on the back on the butterfly forebodes death.

The colours infer purity and naivety, but yet the red in her eyes are symbolic of danger that she may face throughout the film.  The shadowing connotes a sense of suspense and mystery to the audience. The orange/yellow/red tones signify danger and possibly fire.