Define
A single object on a cover that is already the opinion. No headline required if the prop is right.
Mechanism
Metonymy. The thing stands for the verdict. Wit lives in the choice of object, not in a caption.
Verdict
The audience shares the code and will read the object as a sentence.
Don't
The audience will not get the joke, or we still need a paragraph. An obscure prop is a private riddle.