That warning is a eZ Publish permission warning, meaning you don't have access to see them . You can verify this by login with admin user on frontend (if you don't have login link, go to '<site_url>/user/login').
You probably don't have a "content, read, class( image ) section( media )" rule or something (section part depends on where you save the image, class part could be banner instead but it depends on what content you don't have access to).
Go read in the doc about "user roles" and "access rules" if you are unsure what I'm talking about. http://ez.no/doc/ez_publish/technical_manual/4_0/concepts_and_basics/access_control