While remembered for his poster art, Guillaume also did oil paintings such as "Soirée parisienne," a portrait of Parisian dinner society.
During this period, a collection of notable artists helped transform the boulevards of Paris into a gallery of fine art.
From 1895 until 1900, he collaborated with the era's great poster artists to produce a series of smaller works suitable for collectors.
The Maîtres de l'Affiche ("Masters of Posters") collection included the two works below and it was through this series that he became known to a wider audience.
The winner of a bronze medal at the Universal Exhibition of 1900 in Paris, Guillaume had many of his illustrations published in albums by such firms as "Ernest Maindron" and "Librairie illustrée, J. Tallandier" including three albums of military cartoons with the preface for the 1896 edition written by Georges Courteline.