Find the film poster(s) for your case study film poster and then click on the green cross on the side of the poster to enlarge it, etc.
Otherwise find your film posters on the web or in Google Images.
Remember that several posters will possibly have been made for your film, i.e. a teaser poster, the theatrical poster and perhaps a poster with snippets of press reviews or Oscars or awards claimed for it. Think also how some films begin with art-house or minority audiences and cross over into the mainstream (audience-wise) if they become more popular than first expected.