That last point is interesting; in the Bible God forbids his people to make images of him, but artists post-Renaissance chose to depict him. This is a whole new subject, and I am not qualified to talk about Art History. But if God (who is not physical) was made man only in Jesus Christ, would it not be wrong to present the Emperor as a human, a lion, or any other creature?
The creator is always distinct from Creation, in both the Old and New Testaments. To this day practising Jewish people don't like images of creatures as decorations.

Even more so than The Last Battle, I think the lack of references is most noticeable in The Voyage of the Dawn Treader. I know that if I were sailing east in that world, thoughts of the Emperor-Beyond-the-Sea would occur pretty often. "Will we meet him? Are we going to the Empire-Beyond-the-Sea?" So I would definitely expect more references to the Emperor in any adaptation of VDT that seeks to flesh out the story.

Did the Walden Trilogy ever refer to the Emperor? I can't recall any mention of him.

That last point is interesting; in the Bible God forbids his people to make images of him, but artists post-Renaissance chose to depict him. This is a whole new subject, and I am not qualified to talk about Art History. But if God (who is not physical) was made man only in Jesus Christ, would it not be wrong to present the Emperor as a human, a lion, or any other creature?
The creator is always distinct from Creation, in both the Old and New Testaments. To this day practising Jewish people don't like images of creatures as decorations.

That's a really good point. Even aside from the theological tensions, I think there's definitely an argument to be made that any visual depiction could detract from the mystery. That said, you could still indirectly reference the Emperor in art, or obscure the form of the Emperor in some way. When doing a little googling on the subject, I found that the Hand of God appears in Jewish art as early as the third century; I can imagine a depiction of a hand (or golden paw) holding the scepter that Jadis references in LWW.

I think the idea of including visual representations of the emperor in the background is an interesting idea. But I really don't want them to go overboard expanding on this character. It seems like a lot of Narniawebbers want the new series to give Narnia a big complicated mythology. Fantasy franchises like that give me headaches eventually.

I can imagine a depiction of a hand (or golden paw) holding the scepter that Jadis references in LWW.

I like the idea of a mysterious hand-paw holding a sceptre.