Final answer:
A large picture painted directly on a wall or ceiling is called a mural. Unlike other forms of artwork painted on different surfaces or with varied techniques, murals are specifically associated with large-scale, architectural surface paintings.
Step-by-step explanation:
A large picture painted directly on a wall or ceiling is called a mural. This form of artwork has been present across many cultures and time periods. Murals can sometimes be confused with other types of painting such as oil painting, which uses pigment mixed with linseed oil as a binder. Unlike panel paintings, which are created on wood panels and are less durable due to their organic nature, or paint by numbers that are more of a guided artistic activity, murals are typically associated with large-scale paintings directly applied to architectural surfaces. Moreover, murals are not necessarily commissioned paintings, although many are created based on a commission. Murals are known for their ability to portray social events, illuminate with color and are applied using various techniques, including the fresco method, which involves painting on wet lime plaster.