To get a price estimate, multiply the square footage times the cost per square foot. Prices range from $30 to $50 per square foot for wall murals depending on the complexity of the mural  The type of surface to be painted and the amount of preparation required before the I can begin will also affect your total cost. Porous surfaces, such as stucco on an exterior wall , may be more difficult to paint on, which will increase the time and your cost.