I have three custom templates and none of them have thumbnails. Not sure if it's possible; I just renamed each one so I could tell which was which without the images.
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 .