I do not pay too much attention to movie posters, so it comes as no surprise that I have never noticed these clichés before. I guess that the movie advertising business is similar to other design-related fields in that they know what works, and/or are fresh out of original ideas.

Between the legs:

Black and white with colored flames:

 Lying in bed:

 Big heads in the sky over tiny people on the beach:

 Back to back:

Large text over faces:

Blue nature-themed:

One big eye:

 From the back (often with weapons):

The red dress:

Yellow indie film poster:

Reflection in sunglasses:

On a bench:

 

Go visit Le Sibère Carnet de Christophe Courtois (note: site in French) for more!