This element of design is Negative Space. The hand isn't actually holding anything. It implies that there is a light bulb in the empty space. Negative space guides your imagination to finish the image.
Louserit Vuittuun. Luojan kiitos ettei olla kaikki samassa veneessä! 22/2010
I really like how the Surfrider Foundation have represented the effects of plastics in the ocean. Showing the plastic in sushi which is sea food to represent the ocean I think is a clever and very creative way to grab people's attention.