There should be an area where teens can work on things that get a little messy. Not only can STEM learning happen more effectively with hands-on activities, it would just be great to have a space to make things in - something with tools and equipment that serves the needs and interests of teens who are creative and use the library.
Equipment for viewing video, listening to music and gaming should be in its own space.
Space to exhibit teen projects and art works -- both paper and electronic (videos, etc.)
Meeting rooms for groups of 2, 4 or 8 that are easy to monitor!
A place where teens can work on and collaborate on homework, with lounge seating, tables and booths that can easily be moved around.
A flexible space that allows for audio and video recording and editing. (And graphic design.)