Is there any clear picture or drawing, of a Wright brothers' plane, published before August 12, 1908?
I am not aware of any picture printed before August 1908 and showing a fully recognizable Wright plane, beyond any doubt.
As a remark, there exists a drawing, published in L'Auto, a French newspaper, on December 24, 1905, but it is just a rough sketch. However, this caricature is the closest drawing to what would become to be known as the Wright planes, much later, starting with August 1908.
As an explanation: Robert Coquelle, a French journalist, while in the United States for other purposes, visited the Wright brothers, did not see any plane and once back in France he made fun of them in L'Auto in an article titled: &quot;The conquest of the air by two bicycle dealers&quot;. Coquelle does not clearly explain the origin of the drawing below that illustrates his article.

The true aeroplane of the Wright brothers.
Source: 1905-12-24, Robert Coquelle, “La Conquête de l’Air par deux Marchands de Cycles. Comment un ancien champion cycliste, Johanny S. Johnson, introduisit un rédacteur de « l’Auto » dans l’atelier des frères Wright.”, L’Auto, Paris, Saturday, December 24, 1905.