I love trompe l'oeil! Here we have a realistic fellow poking his head through a canvas, and seeming to declare that a resemblance is guaranteed.
The artist is unknown, but it's thought that this is taking a dig at photography; "Resemblance guaranteed" was almost a cliche of early portrait photographers. The paintbrush in his hand, and the fact that he's looking at us through a canvas, I think tells us the artist is in favor of painting.