Cooee, my understanding is that these visual stories were known and understood, so no note was needed. It was meant as visual storytelling, so, really, adding a sign would defeat the purpose. For instance, if you had a guy with an arrow sticking out of him, you knew it was St. Sebastian, and if he had stones at his feet, it was probably St. Stephen. If it were a nonreligious topic, there would be hints, and people who saw it would presumably know who was in it and what it meant because they were in more private places. For instance, I saw a tapestry at the V & A depicting a hunt, and the figures in the tapestry represented real people (the ones who commissioned it). If you were a guest or a servant, you could probably piece out who was who. If not, somebody might be there to enlighten you. They were usually put in private or public/private spaces. Something like the Bayeux Tapestry was meant to be more public, and it does have what amount to (Latin) captions woven into it, doesn't it?
That could be a small point for your character, who puzzles over a tapestry they see, or who just loooves to tell everyone all about the wonderful tapestry on their wall.
