These are from a series of paintings called Creation of the World, by Lithuanian symbolist artist and musician Mikalojus Konstantinas Čiurlionis (1875-1911), who's a new discovery for me. The entire series can be seen here, along with many more examples of his work.
The Bohemian artist and writer Alfred Kubin (1877-1959) is another neglected figure from the early days of Modernism. Inspired by the likes of Goya, Max Klinger, Odilon Redon and Félicien Rops as well as Gogol and Poe, he created hallucinatory, proto-Surrealist images before developing a style more akin to Expressionism later in life and exhibiting with the Blaue Reiter group. His drawings were mostly executed on a certain type of highly absorbent land registry paper - his father was a land surveyor - and he claimed he was unable to work on any other variety. Kubin also wrote and illustrated a novel, The Other Side (1909), which is currently somewhat out of my price range.
The Italian Futurist Fortunato Depero (1892-1960) tends to be overlooked these days for some reason, which is a shame because the best of his work easily holds its own against that of Boccioni or Balla. He was also one of the most versatile talents to emerge from the movement, turning his hand to painting, collage, graphic design, sculpture, tapestry, theatre design and toy-making. The images above are from Fortunato Depero: Carnival of Colour by Roberta Cremoncini.
Of course, I'm not the first person from around these parts to take an interest in this stuff...