So I learned how to do the Warhol technique through this wonderful tutorial: http://www.photoshopsupport.com/tutorials/or/warhol-pop-art-silkscreen.html
In my opinion, the more color you can bring into individual areas the better. I know you photo students were looking into how this is done, if you have time this summer give it a whirl. Select a photo with some mood to it. It should be zoomed or cropped into just the head and shoulders.
The mood I selected was cheeseball :D
I want to thank my wonderful husband for participating. Check out his work- he is amazing www.nicholasviltrakis.blogspot.com