Bumi Parahyangan promotional poster and brochure by Rittsu, at Behance. Triangles don& seem to be popular shapes to use in graphic design, but Rittsu executes them well here. Notice the subtle arrows pointing right to persuade the viewer to read on.
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.