The block itself cannot be removed from the chain but the content can. You can go back and edit any post and delete all of the content and you will be left with an empty post.
The images are not stored in the blockchain. If you are using the Steemit.com website, they are stored in Amazon Simple Storage Service, also known as S3. The images can be removed from S3 with a DMCA take takedown request. So images are not indelibly ingrained in the blockchain, nor is the text and links in a post, which is good for all copyright holders/
That explains it well. Thanks!