Humans are essentially visual creatures. Iconic representations will help teachers and students quickly realign their synapses to the question at hand. Please give admins the option of showing a cateory icon by the question.
adding a field for the URL for the category icon
adding a script to the mod/quiz/attempt.php?q=XXXX quiz interface to pull the category icon URL and display it
adding a script to question/edit.php?courseid=XXX to pull the category icon URL and display it