If I were you I would Google free stained glass patterns and start looking there. You will probably want to use some of the colors in your furniture or acc. You can enlarge the patterns to fit what ever your transom size is. Good luck. Pics would be great and welcome to the forum.
Carol

You could do a Glass on glass, which is very do-able and fun yourself, if you don't do traditional stained glass work. It's where you take a window, or pc of glass the size of the opening, and create what you'd most like to see there and glue the pcs on, then grout it, here is an example of one, it is my front door window....

Here is a link that might be useful: