When I did my small stained glass wall hanging, I used blue fabric that looked like sky when looking out the window. So I would take a good look at what you are going to be sewing & really 'scope' it out. Now some stained glass quilts I have seen only have the black Kona cotton behind them. I have found that I can get Kona cotton at Hobby Lobby for a really good price but if you don't have a Hobby lobby close by I know you can order from Hancocks in Paducah KY