Optical illusions are great works that cleverly utilize the ambiguity of positive and negative spaces. One great example is a poster for the Disney film, Brave.
In this poster, there is an influence of Yin and Yang concept, where both negative and positive spaces have forms. Each space becomes a negative space to enhance the other one into a positive space. In this example, Merida’s hair shapes the form of a black bear, while the form of the black bear creates the form for Merida’s hair.