The very use of non-realist signs can (but does not necessarily) put representation (the code of signs that connote realism) into question.  This particularly true of highly subjective paintings like "The Cry," but also of some of Cezanne's paintings.

The use of self-aware signs can also put representation into question, although it does not necessarily do so.  Indeed, "Las Meninas" uses self-awareness of the act of painting to reinforce representation.

"La Condition humain" uses self-awareness (a painting of a painting) to put representation into question in the following ways.

1. It places the painting on an easel, the painting represents itself as a human product, an artifice.

2. Since it places the painting in front of the scene painting (the object of the painter's and our gaze) and creates a confusion between the painted scene in the real scene, "La Condition humaine" might be interpreted as saying that there is no difference between the artificial representational work, the painting, and its object, the natural scene. 

However, because the painting in the "La Condition humaine" represents, not real nature, but rather a scene that is also in "La Condition humaine," and because "La Condition humaine is an artificial pictorial representation, we in fact have an artificial representation ("La Condition humaine") of an artificial representation (the painting on the easel), of an artificial representation (the beach in "La Condition humaine").

4.  The confusion between the painted scene and the real scene suggests the confusion between representation and reality that takes place in all realistic representations, including our consciousness of what we see.  

5.  The Escher paintings are also self-aware, although they do not refer directly to the act of painting.  They too put representation into question.   What aspect of visual representation do they put into question?