1. Go to PlatformUI;
2. Create some image content, and publish it;
3. Create a content type having a RichText field;
4. Back to "Content Structure", create a content of the content type you just created with Rich Text field;
5. Add the previously create image content to the Rich Text field, using the <embed> embed option, instead of the <image> embed option;
6. Publish the content;
7. The image will not display neither on frontend nor on backend.