Traditional lampshades are upholstered in artists' canvas, and the inner surface is then painted.
Here's some text from Ryan:
‘UNTITLED’ Lights By Karen Ryan
I have had a love affair with painting for many years, ‘UNTITLED’ lights mixes this love with my other obsessions of design, graphics and fine art.
Untitled are paintings that are internally lit, I use the familiar scallop standard lamp shade as my canvas. The lamp shade has been made larger than normal 18 inches 23 inches and its internal light fitting redesigned for its new life.
The scallop shade is primed as tradititional canvass is with gesso, its structure is made opaque so that no light penetrates its form but instead lights the thickness and stroke of paint marks and colours.
I light colour rather than colour light. I abandon my artwork to the floor or a table.