"To paint a mural" means to create a large and colorful artwork on a wall or surface, usually outdoors, to tell a story or express a message. Full definition
My friend once painted a mural on part of the low ceiling in her kitchen. (theinspiredroom.net)
I would consider it an honor to help in an artistic way (I have painted murals in local schools, hospitals and homes) if you need my help. (theletteredcottage.net)
He then painted a mural of an open mouth. (insteading.com)