I love this topic and will happily check back in on the regular, in case you share more.
I found a bunch in The Killing Joke that I shared ages ago, but I’m not sure where the post is. I can dig it up sometime. (And its examples might not count as symbolism, but they were great artistic choices).
It’s based on the lost boys film by Warner brothers. It has a lot of hidden symbolism as well. For ex: David, Star, Bottle of blood, Joining a ‘club,’ etc.
I can’t remember where I heard/read it, but during the 1960s DC creators took great pleasure in sneaking in a certain image in Supergirl and Wonder Woman comics.
I can’t remember the details well, but that movie was way better than I expected! Not sure about accuracy, but the subject matter was handled in a mature way rather than exploitative.