There's a couple movies that I'd like you to watch as a theme:
Fear and Loathing in Las Vegas
In the first movie (Tideland) we discover a child's imagination... a very innocent kind of imagination and a very experimental movie (as you will realise that all Gilliam's movies are). This movie will paint a very beautiful picture of childhood imagination, and it's certainly worth the watch!
The second movie (Fear and Loathing) is a little different however and has lost it's innocence! The imagination in here is stimulated! And stimulated by drugs! The movie as a whole is really funny, and Gilliam experiments with Imagination in a not so very innocent manner! Really interesting movie, and extremely funny in parts!
The 2 movies together will give you a great view of imagination, and what it means to a lot of people.
So start imagining you had this movie!