Giger finds out about the Nigerian synth-funk pioneer William Onyeabor album Atomic Bomb most likely from Bolaji Badejo who came from Nigeria, and then associates the oddity of the surname Onyeabor with name Hieronymus Bosch since they share the letters ONY and BO in the same order, leading him to merge the cover photo with a demon from Hieronymus Bosch's Garden of Earthly Delights.
Uselessly, William Onyeabor + Hieronymus Bosch + Erebor = William Hieronyeamus Ereborsch!
What else is there to find in the image?
Perhaps the face of a Japanese Oni transformed into a Heike crab and there's The Big Top to consider
a) HR Giger: Demon (work 413) references Onyeabor's image from Atomic Bomb album cover?
b) HR Giger: Demon (work 513): William Onyeabor transforms into Hieronymous Bosch
c) The Big Top
d) Tolkien's book cover for The Hobbit
e) Connections with Arnold Böcklin's Island of the Dead 3.
Since he was a fan of the artist, I might also wonder if Gigr was thinking about one of the Arnold Böcklin Island of the Dead paintings, such as the right side of no.3 which would have a doorway where the nose of the demon was, connecting that with where the doorway in Erebor in the Tolkien book cover for The Hobbit would be found. This perhaps would mean that he was making a BO connection between Böcklin, Bosch and Onyeabor and the Big Top was near enough to the German for Island of the Dead being "Die Toteninsel" with Top and Tot.
|Böcklin's Island of the dead 3|
|right half of painting reflected|
f) Oni and Japanese Heikegani crab
Another thing to point out is the word Oni in Japanese is a sort of a demon and the Japanese produce Oni masks, but I haven't seen one on the internet with anything in common with this face, but I wonder if Giger was thinking of one of those. And then thinking along the idea of something Japanese, I suppose the general structure of the thing resembles a Japanese Heikegani crab which has a face like form on the shell. Here's an image of one of the crabs, which is something we've come across before in Giger's painting, The Spell III.
(See also: Giger's The Spell III)