if you have the book New Moon, go to the acknowledgments at the front. At the very end she thanks a load of bands including mcr. (dw i don't read new moon still i have it from when i was younger. just thought id mention that)
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.