Remy de Gourmont (1858-1915) was a french symbolist poet, novelist and influential literary critic. Two of his works, the so-called Livres des masques, (books of masks) are critic-literary anthologies illustrated by Félix Vallotton, a contemporary of Gourmont. His monogram appears beside each portrait. Vallotton may be little known today, but he was very influential in later artists who worked in simplified and stylized shapes, with big contrasting masses in the images.
The portrait gallery includes Francis James, Marcel Schwob, Maurice Maeterlinck, Stéphane Mallarmé, Lautréamont, Arthur Rimbaud, André Gide, J.-K. Huysmans, Paul Verlaine and many more.
The books of masques are available for free on Project Gutenberg. (http://www.gutenberg.org/browse/authors/g#a6996). They include the aforementioned portraits by Vallotton in bigger sizes. Those images can be vectorized very well, for example with Inkscape: