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.
Durex ad for condoms. White background with blue logo. Upstanding condom on 1 side and baby nipple on other side. Protected sex or baby- simple photo image conveying powerful message about choices and consequences.
Don't text and drive: you either see the letter or the danger. This is a fantastic example of how clever use of space can make a big impact. An innovative idea that really drives home the dangers of while driving. by Leo Burnett for FIAT
Ice Cream Poster - Fantastic, double printed, posters designed for ice cream Kibon, by the designer Renata El Dib. Posters represents reminds one side of the texture of an ice cream and the other one to the ice cream cone.
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.