Need Ideas for Summer Camp

Every summer, TSTC hosts a camp for high school students (ages 14-18) that teaches them about technical careers. It's a 3-day, 2-night camp. Last year we divided the students up by classification (9th grade, 10th grade, 11th grade, 12th grade) and assigned them colors (orange, blue, etc.). This year we want to take it even further and have a "theme" for each group...problem is I can't think of any themes to use....any ideas?