For those of you who can't paint, here is a simple technique.
Total Time: 2 hours
assorted acrylic paint
oil based Sharpie marker
piece of glass
Print a picture (stained glass) from the internet or another simple picture to fit the size of the glass. Tape the picture to the underneath side of the glass.
Using a black Sharpie, outline the design. Let dry for an hour. Using a thin tip paint brush, begin coloring in the spots within the black borders you have previously outlined. Let dry thoroughly. Add a second coat if necessary. (If necessary to fix a mistake, you can dip a q-tip into nail polish remover to remove paint.)
Spray varnish to help make the paint more permanent and to prevent it from coming off of the glass.