AS Photo - For your theme 'Mystery and Imagination' you might want to look at Wendy Ewald's project 'Secret Games'. As a start you could also look at Tim Walker, Anne Geddes, Rankin, Francis. J. Melhop, Cindy Sherman, Michael Hallet, Zena Holloway and Lois Greenfield.
Edgar Allen Poe wrote a book titled 'Tales of Mystery and Imagination'. Perhaps you could read this for some inspiration ideas!