Those are kind of cool. I think your thought was correct-ish.
The Toy Story one is awesome because the little alien guys are easily the best part of that entire franchise. I love them.
Why did they fold the posters?!
The hourglass sand in Prince of Persia looks rather like a martini glass.
I think the Titanic one is the best. There are definitely a few levels of meaning there.
Banana Nut
There are some cool posters here:
http://visboo.com/creative-movie-posters.html