It depends entirely from what subject perspective you want to approach it.
If you're taking art for example it could be on the changing perception of beauty in portraits through time.
If you're taking psychology for example it could be on people's perception of beauty at different ages, for example showing a range of people of different ages different pictures of women and asking them to rate their beauty on a scale of 1-10.
Just two random ideas but as you can see it will be very different depending on what your subject interests are. Perhaps ask the teacher for the subject in question (art, psychology, etc) if they could help narrow your ideas down?