Turned applique would be stunning. That way it would be easy to form the various shapes, and the quilt would have a refined finish. Reverse hand turned would even more exquisite!

How accessible is the panel? And how large?

Would it be possible to tape some freezer paper over the whole window, and then draw round the colour shapes? You could then cut out the colours using a craft knife, leaving the background intact. Iron the background paper to your background fabric. The holes in the template would let you place the colours exactly, and then aplique using your favoured technique.

This would give a finished product the same size as your window, if that's what you want.....

I would applique it too. Seems the easiest route if you want an exact replica. There would be a million seams if you paper pieced it, especially due to the rounded corners on those squares.

Wow ... this is exactly why I asked for your help. All great suggestions and various options to try. Can't thank you enough. I'm thinking I may take some of my scraps and play around with several methods to see what works best for my skill level before starting on the actual quilt. Thank you all!!! I had just looked at this picture so much, I couldn't figure out where to begin with creating a pattern.

Make yourself a pattern on a light box or draw up your own design, use adhesive backing and just put the pieces of glass design onto a black rectangle of fabric then do some straight sewing around each piece of glass.

Personally, I would probably try to make a straighter version of the stained glass. It looks like an old window & often with stained glass repair, the welding repair results in the metal frames becoming slightly larger. Over the years, it builds up creating an irregular shape.

I love all the ideas everyone here has suggested. One other option would be to do it reverse applique. I think a piece of black felted wool on the top with bright breezy batiks peeking through could well represent the stained glass & account for the irregular shapes. I agree with Lizzy that making a paper pattern & transferring that to your black fabric would help regardless of which method you use.

Or if she wanted a smaller or larger size - start with the traced pattern - and then it could be copied on a copier that has reduction or enlarging capabilities.

Are there any places that can copy really large things? I know some drafting/engineering/architectural types of places have copiers with fairly large capabilities.

It could still be dealt with in strips - see QuiltnNan's drawing - I think the reverse applique would give the most realistic effect.

What an exciting inspiration piece to try to replicate in fabric! Can't wait to see what you do with it, nor have any different suggestions to offer.

I agree with others here that suggest applique. I would do a black background then use steam a seam 2 then raw edge applique.

Applique would work, that way you could make the rows wider in places and narrower in others. In the areas you have to put white, you might look at silver. That way you get the shine and the light color, without the black showing under the white. Good luck and don't forget to post pictures.