As a director I like to keep a solid hand in the creative process as possible. Most directors are are unable to completely storyboard a film by themselves and they have to rely on building as solid a crew of artists and designers around them as possible. One of the ways to help define your vision of the the story is to simply break down the script into it's key points of interest. Then you illustrate the key images as best as you can imagine they are going to unfold on the screen. I keep things rough at this stage, I usually have a great deal of organizing to do and time is always important. With these rough illustrations I can then delicate the actual designs and ideas to the artists and then let them add their input on the story images for design and storyboard.
STORY IMAGES FROM "THE INVINCIBLE IRON MAN"
STORY ILLUSTRATIONS FROM "HULK VS. THOR"