Examples of visual forms of communication?

Visual forms of communication would primarily focus on the recipient's use of eyes. An example would be gestures such as expressing "OK" with the index finger meeting the thumb, or expressing agreement with the nodding of the head or disagreement with the left to right movement of the head. I also think an example would be billboards or electronic signs that communicate information to drivers. If it is strictly visual - no other sense (hearing, touch, taste) would be used in the communication of information.