Simply having more variety in both students and teachers. For teachers, having differing hair styles, and for both, having more alternate bust sizes (at least a larger one for students and a smaller one for teachers) and skin tones (at least dark skinned both with and without tanlines).
If you add in male students and teachers, the ability to grab two people and put them in same locker to 'pair' them might be neat. This should be a toggle for the menu, though.