Scooby-Doo Zombie Island (Fan Made Prequel Poster)

I love Scooby-Doo and my favorite movie is definitely "Zombie Island". The story, the characters, the design...everything. So I decided to make a poster for an imaginary movie called "The Moonscar Island" - starring Nicole Kidman as Simone Lenoir and Jenna Dewan Tatum as Lena Dupreé. The movie would follow the two ladies through the ages before the Scooby Gang arrive in the island.
I'm not used with this kind of thing (manip) and I know it's not perfect, but I hope you like it.