Just a few thoughts, hope these aren't duplicated:
-- A dictionary for acronyms: UFO, PIGS, etc.
-- A good description of different types of batting and how to select the best for a project
-- A list of "repurposed" sewing tools: chopsticks for a stiletto, etc.
-- A section for finishing the edges: wrap to the back, wrap to the front and simple binding instructions with a special emphasis on corners.