If you want prompts based on quotes, then here are a few to get you started:
"He had no money and no home; he lived entirely on the road of the racing circuit, sleeping in empty stalls, carrying with him only a saddle, his rosary, and his books....The books were the closest thing he had to furniture, and he lived in them the way other men live in easy chairs."
A good prompt based on this quote would be: "Passion and hunger are the best ways for a man to achieve his dreams." This is a prompt that you can take in so many different directions, especially in stories that feature an underdog. Also who does not like a good underdog story? This will afford your essay many examples from the book.
Here is another quote:
"In 1938... the year's #1 newsmaker was not FDR, Hitler, or Mussolini. Nor was it Lou Gehrig or Clark Gable. The subject of the most newspaper column inches in 1938 wasn't even a person. It was an undersized, crooked-legged racehorse named Seabiscuit.”
A good prompt for this one would be: "Sometimes what grips the imagination of a people is the least expected thing."
The beauty of this prompt is that you can show how a horse, owner, and rider can be catapulted into the imagination of the general public. From this perspective, you can look at the historical context. By doing so, your paper can have a historical and sociological twist. You might want to start thinking about what made the story of Seabiscuit so great? What moved a generation?