I've already seen past paper questions (at school can't find them online) on natural order, Edmund, Edgar and Cordela together about resolving the tragedy, Gloucester, hopelessness at the end and madness... So maybe women or family relationships? Importance of minor characters?
I'm doing Tis Pity with Paradise Lost and I'm hoping something about emotion vs logic, wrongdoing, desire... Something like that. But they're pretty standard every year.