An awesome light sculpture by Valerie Boy, on the Apartment Therapy website.
Photo courtesy of http://www.apartmenttherapy.com
This uses powder-coated metal which is cut out around the edges of the pattern to produce a halo effect – very detailed work and a great idea!
An easy way to achieve a similar effect would be to cut out multiple stencil patterns which are then stuck on a canvas, with a darker (or non-transparent) paint layer sprayed over. Once the stencils are removed the spaces would let the light through – slightly more rough than this but probably quicker : )