Traditional stained glass windows are seen less and less often and are usually contained to churches and old buildings. They are still, however, beautiful and a good source of inspiration for designers.
The way the light interacts with the colour and patterns within them is effective and something you could experiment with by drawing designs on transparent materials and layering them up against a light source. This will allow you to test out different combinations of designs and to gather a lot of information quickly. Take into consideration that when you are exposing your designs to the light source, interesting shadows are often created which in their own right are effective, providing you with a whole other set of patterns!