u can't.
In most quizzes, the Prizes afbeeldingen are the same, because they are generated door Fanpop.
See the default prize lijst
link But, on some kwissen like the Twilight of the Harry Potter quiz, the prizes afbeeldingen are different because the F4 made those custom prize sets.
But, if u want to know meer about this see
link artikel (there may be something in there about changing the kwis prizes afbeeldingen ;D).