Go to revise item and right click the photo and hit the cut tab and it is gone.Then save the revised listing.Inserting a new photo however would be much more complicated unless you use eBay hosting for it.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .