As I was going to the museum yesterday, another idea for a display hit me. Perhaps we could do something with antennas. The display could explain the different types of antennas (dipoles, verticals, beams) and why some are longer and some are shorter (the concept of wavelength).
If we had a computer screen big enough and accessible to the public, all this could be on-screen, and if the display was some kind of touch screen, it could even be made interactive somehow. This is something that could be running when we’re not there.
This is just a partially-baked idea, so please feel free to chime in with other ideas.