I watched the film maybe more than a decade ago, what is he so surprised, shocked or in awe about?
There was a MacGuffin suitcase the main characters of Pulp Fiction need to recover because it's important / valuable, but the viewer never learns what's inside it. At the end of the movie Jules peeks into the case and we get that golden glow effect, and see this reaction, but the viewer sees the case from behind the half-open lid, so we never get to learn what it was. Perhaps the artist is implying it was a cheeseburger.