According to the author himself "The Dark Tower" is Stephen King's most important work. The story has developed for the last 30 years as a fantastic mix of fantasy, western, horror, science fiction and romance and therefor has all the ingredients needed for a successful cinematic adaption. Since 2010 director Ron Howard is working on a way to produce a film adaption of the complex story – unsuccessfully. After Universal has dismissed the project as "too expensive" Warner Brothers has announced their interest in a film in spring 2012. "There's life in the old dog yet!"
Stephen Kings official website offers basic information on the series "The Dark Tower" featuring all the important artwork. This piece of art by Dave McKean is taken from the illustrated book "The Dark Tower IV: Wizard and Glass". MARVEL is King's US publisher for the Dark Tower comic series in the States.
Source: Dark Tower Official Website (http://www.stephenking.com/darktower/the_artwork.html)