LockDown Browser does not cache images (like a standard browser does) and overly large images can result in problems with LockDown Browser loading the page. When such an image is detected, LockDown Browser replaces it with the above image file.
Instructors and web designers should reduce the size of all such problematic images. A size of under 9 megapixels is necessary (A resolution where width x height is less than 9 million). Once the image is resized, LockDown Browser should be able to display it.