I agree with the picture. The other explanation as Lucy being a Gryffindor, Susan a Slytherin, Edmund a Ravenclaw, and Peter a Hufflepuff I see the point but I feel like the original picture here is perfectly assigned.
Lucy Pevensie: A girl who didn't stop believing things just because people told her they weren't true. A girl brave enough to live by faith. Quote from Lucy "I wish you'd all stop trying to sound like grown-ups. I don't think I saw him, I did see him.