Help images are not displayed

Hi, I am using gitlab with the apache config from gitlab-recipies. My problem is that none of the images on the help pages is displayed. Every image causes an 404 or an 500 error.

Started GET "/help/workflow/notifications/settings.png" for 12.34.56.78 at 2014-11-04 18:11:45 +0100
Processing by NamespacesController#show as HTML
  Parameters: {"id"=>"help/workflow/notifications/settings.png"}
Completed 404 Not Found in 6ms (Views: 0.7ms | ActiveRecord: 0.7ms)

Started GET "/help/workflow/four_stages.png" for 12.34.56.78 at 2014-11-04 18:27:29 +0100
Processing by HelpController#show as PNG
  Parameters: {"category"=>"workflow", "file"=>"four_stages"}
Completed 500 Internal Server Error in 5ms

ActionView::MissingTemplate (Missing template errors/not_found with {:locale=>[:en], :formats=>[:png], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby, :slim, :coffee, :haml]}. Searched in:
  * "/usr/share/webapps/gitlab/app/views"
  * "/usr/share/webapps/gitlab/vendor/bundle/ruby/2.1.0/gems/semantic-ui-sass-0.16.1.0/app/views"
  * "/usr/share/webapps/gitlab/vendor/bundle/ruby/2.1.0/gems/kaminari-0.15.1/app/views"
  * "/usr/share/webapps/gitlab/vendor/bundle/ruby/2.1.0/gems/devise-3.2.4/app/views"
  * "/usr/share/webapps/gitlab"
  * "/"
):
  app/controllers/application_controller.rb:140:in `not_found!'
  app/controllers/help_controller.rb:12:in `show'

Is this a gitlab issue or a webserver misconfiguration? I have tried Passenger as well, the problem stays the same. So it may not be a unicorn issue.

edit: The development-kit setup does not show these images as well.