The swords illustrate the seven basic "strokes": six in a "flower", and one stab (the bottom one). Mastering all of the ways to get your weapon from point "A" (near you, in a proper guard), to point "B" (somewhere inside of your opponent), through one of these directions, is the purpose of the book.
As a serious answer... the image characterizes the qualities of the warrior by relating them to animals: Attentiveness (jackal), Speed (tiger), Strength (elephant), Courage (lion)