Well, time to start getting a bit creative about who I asked. John Clarke is a writer and comedian.
Thanks for your inquiry. It is little known that I provide an advisory service specialising in the iconography of Bob Hope movies of the middle 1940's.
I suggest you ensure thare is plenty of rubbish under Richard's bed, since you may need to play for time while working out how to make the following appear interesting.
The lily is a symbol of purity, it says here, and is normally associated with the Virgin Mary, evidently a religious figure of some sort. It features in conventional representations of the Annunciation and, as I'm confident you will explain to Richard, this is why it's so funny in the Hope movie. The only suggestion I would venture with regard to selling a simple version of this to the inquiring minds of junior staff, is that it be pitched as a sign of having lived a good clean life, worthy of favourable consideration in the event of a stratified afterlife.
Should Richard not be satisfied with the generality of this response, recommend him to Brewer's Dictionary of Phrase and Fable, or Hall's Dictionary of Subjects and Symbols in Art, each obtainable froma library I would think.
I note that you have three sons. I suggest you lay in copies of all available reference works immediately. Good luck.
Best wishes, John Clarke.