The yearbook for Bates High School is seen on screen. Bates High School is famously known as the high school attended by Carrie White in the film version of Stephen King's novel 'Carrie'.
A lookout called King's Point is mentioned. A nod to Stephen King who wrote the story the series is based on.
Nathan says the black substance was "atomized graphite", "willow charcoal and a little clay". The authors have confused two sketching tools. Graphite pencils, which give hard clean lines, are a mix of graphite (a mineral mined from metamorphic rock) and clay. Charcoal, willow is the favorite, is made by heating wood sticks to over 500 degrees in the absence of oxygen and gives soft smudgy lines. It's possible the artist used both kinds in each of her sketches.