In Disney+'s The Mandalorian, each episode ends with concept arts during the ending song. I don't know if this is a new film technique or not, but I've seen in first in RWBY and now in The Mandalorian. Where did it originate from?
Pixar, and later Disney, have used end credits to display alternate art and/ or storyboards. The first film I can find that does this is WALL-E, although in that film the end credits continue the story rather than retelling it.