It may be a novel, comic book, old film, or idea. But someday it COULD be a movie or TV show. Find a story you would like to make casting suggestions for, or suggest a new one.
Once you've found a story you're familiar with, browse the characters or add a new one. Who are the main players in the story?
Now, think of the perfect actor or actress to play the role. Type in their name to suggest them, and let others comment their thoughts!