Since SpeedGrader does not show previews of uploaded images in a quiz when instructors are grading, we use the essay question type and ask students to embed an image. This way, they see a preview when they are working on the quiz, and instructors can see the image when grading without having to leave SpeedGrader.
The issue is that this embedded image is a link and not a file itself. So if a student submits their quiz and then deletes the image, an instructor cannot see their work. Further, it doesn't seem that anything would prevent a student from changing their image after submitting the quiz, so they would be able to change their answer.
When grading, there is even a message that states this when hovering over the image: "This is an image, not text, and could have changed since the student submitted."
I would like a file embed to behave like a file upload in that the quiz contains a copy of the image which cannot be removed or changed by the student.