His first comprehensive suite of illustrations appeared in Stories for Pictures (1912). Further commissions followed, in the form of his illustrations for Fairy Tales from Hans Christian Andersen (1914),Dream Boats and Other Stories (1918), The Wishing Fairy's Animal Friends (1921), Rainbow Gold (1922), Snythergen (1923), The Six Who Were Left in a Shoe (1923), Many Wings (1923), The Dust of Seven Days (1924), Squiffer (1924), The Golden Porch (1925), Orpheus with his Lute (1926), Mopsa the Fairy (1927) and Go! Champions of Light (1933).
Walker displayed an outstanding eye for colour and was also superbly gifted throughout his detailed monotone illustrations. His own Foreword to Fairy Tales from Hans Christian Andersen (1914) provides some insight in the beautiful soul that created such wonderful images - part of that Foreword follows:
"I have never been anywhere except Richmond, Virginia, and New York, because I have always been told that only grown-up people were allowed to travel. But the good East Wind and the kindly Moon have taken me on rapturous journeys high above the world to get an enchanted view of things. In this book I have put some of my discoveries, but if you are looking here for real likeness of the things that any one could see if he were grown up, you had better close the covers now. You cannot expect me to draw an exact picture of the North Pole or of a Chinese lady's feet or of a sea-cucumber. But if you are interested in what the East Wind or the Father Stork or the Moon told me, then look with my eyes and you will not mind very much if the courtiers in the ogre's court, or the dock leaves in the Garden of Paradise, are not just as a grown-up person thinks they should be. After all is said and done, what the young ones say about it is the all-important matter."
Text from Spirit of the Ages Bio