My BFF wanted to have some light-up eyes for a costume that she's making, specifically ones that would react when she spoke. So I made her this little assembly, which holds some round LED boards a nice distance away from some LED black acrylic. I'm driving them with WLED running on an Adafruit Mini Sparkle Motion board so it can be powered off a battery pack. The built-in mic means she can have her voice-reactive eyes too!
https://www.printables.com/model/1320889-light-up-eyes-assembly