Here's a large and impressive luminaire I designed back in 2018. The complex voronoi surface casts mesmerizing shadows across the room. Designed for 400 mm print beds and printed without supports. I suggest using a small layer height for better handling of the small overhangs (around 0.1mm layers).
The structure is fully enclosed with a 44mm circular opening, so it requires a narrow bulb that can fit through the hole. I used the IKEA Hemma cord set for the fixture, which threads into place. Fastening a different cord into place may require some ingenuity!
For best shadows, use a clear (non-diffused/frosted) bulb. I used these, which worked quite well, but the smaller the light source the more crisp the projections will be.
Photographed model was printed using MatterHackers PRO PLA (Emerald Green)