Typically, if you're prototyping something and you need part of that prototype to illuminate, you have to design around whatever off-the-shelf lighting component you're using. The available technology thus influences the final form.
What if, instead, you could 3D print whatever shape you like, and spray the lighting on afterwards? I know that sounds crazy, but a group of HCI (Human Computer Interaction) researchers at the UK's University of Bristol have figured out how to do just that. They use multimaterial 3D printing to print a combination of insulating and conductive plastics, then spray a series of materials (including one layer of electroluminescent paint) onto the form and wire it to a power source.
Here are examples of what they can produce:
They call their process ProtoSpray, and here's what it looks like in action: