I filled the top with fiberfill because my wool fabric was just big enough to make a pouch to cover the top of the opening of the teacup using the saucer as a pattern for my circle. You could certainly use crushed walnut shells in the cup or emery if you wanted and cover it. I used hot glue to glue the fabric on the top, but the hot glue didn't work to glue the cup to the saucer so I had to get some all purpose craft glue from Walmart to glue the cup to the saucer.
Have you seen the teapot lamps someone makes on Etsy? The run about $100.00 but they are ultra cute. Unfortunately they are too fragile for my home where my cats regularly knock over lamps during the gymnastics.