I decorated my cap in high school. It was a pretty big thing to get it airbrushed at the time. I had a white cap and gown, and I had airbrushed 2002 and panther paws in purple (my school's mascot and colors). Some people get really creative. I like the trend.
Plus, I graduated high school with more than 700 people, so my parents had a much easier time finding me in the crowd
I honestly don't even know if we could have decorated our caps in college. I don't remember seeing anyone who did it when I graduated.