After reading amitjain123's new thread on the subject of stained glass, I went hunting in the RWS Forum Index and found this thread. Besides the neatly hidden word PAX in glass of the Four of Swords, I had a couple of other thoughts.
Until the invention of the Gothic arch, churches and cathedrals were dark, dismal places and were lighted by candles. Their large, heavy size made windows impossible and what windows there were amounted to small slits. It was the Gothic arch that made large expansive windows possible. When the windows were filled with stained glass it must have been a magical experience, almost like being in heaven. The secret to making stained glass was carefully guarded. It was made by adding metals to the glass which produced the color. But it couldn't be just any metal, you had to know which ones and in what combination to produce the desired color. So symbolically there could be an alchemical connection.
Waite comments on the Four of Swords, "
Divinatory Meanings: Vigilance, retreat, solitude, hermit's repose, exile, tomb and coffin. It is these last that have suggested the design." "Tomb" and "coffin" could point to Rosicrucian symbolism.
I think the light streaming through the windows is highly symbolic. The secret orders are all about finding it. It seems to me there could be Masonic and Templar symbolism woven in.
Two simple cards rich with symbolism.