Shape
The arrangement of negative 
shapes dramatically affects how we perceive the positive shapes and the overall balance of the composition. If the negative shapes are symmetrical, then the form will have "stable balance." If the background is asymmetrical then the positive shapes may display "dynamic balance" --  a state in which forces are in equilibrium but seem more active.  If the negative spaces are very angular or complex, then the positive shapes may appear to be in motion or an illusion of depth might be created by the implication of perspective.