My wall sconce originally came with clear glass tea light cups. I wanted something a little more unique, and something that would diffuse the light better, so I replaced them with 3d printed cups.
I printed them in glow in the dark PLA. This PLA has a beautiful rainbowy sheen when you shine light through it, and of course it glows softly for a while after I turn the lights off. Lovely. I love the scallop pattern that's thrown onto the wall by the ruffled edge.
This is a remix from Marco Alici's Koch tealight design on Thingiverse. I made it a little smaller -- the 4cm height fit better into my sconce.
Or, find a design on Thingiverse for your own creative delight.