Take a look at my 'Glass Rainbow Window Hanger' for instructions on cutting the glass and wrapping the edges with the lead.

Take some nice greeting card stickers and stick them on to your (clean!) glass.

Color them in with glass paints. It's a bit tricky to get all corners covered yet not to spill on the sticker itself.

UPDATE:
I finished the fairy and the cats and combined it with a nice stick found in the park nearby and the rainbow window hanger I made earlier (see other project of mine). I added two (crappy) pictures of the final result.