If it comes to light novels there are always some pictures that show a new character or scene. But when it comes to a character, who decides the design? For example, if I were an author and my work gets a publisher, then they would hire an illustrator. So when it comes to the design of a character (let's take character as a simple example) will the publisher decide that her hair is short and red or will the author decide that she has long, black hair? Also feel free to tell me some other example like maybe the illustrator can choose the design. :)
Mainly the illustrator does.
Basically writers are not involved in design. But he or she can tell the hope to the editor.
It is an example of making a light novel.
- An author write up the novel.
- The author passes it to the editor. (Perhaps they will talk about what the author wishes at this time, like illustrator desired by the author, places of illustation and so on.)
- the editor orders illustrations for a illustrator.
Then he tell the illustrator the atmosphere of the work, distinctive features of charactors like age, hair hength, shape of weapon, chest shape, etc...)
The editor reads the novel before ordering of course. So the content of the novel and the illustration rarely differ.
- the illustrator sends rough sketches to the editor.
And the editor shows them to the author.
- Then the author and editor modify sentences and the illustrator completes the illustrations, the publisher promotes the release date of the novel.
For answers, I referred to the remarks of an actual writer.(Written in Japanese.)
He says that "It is often better for the editor and illustrator not to speak to the design."
Many writers respect the illustrator. And it seems that they trust work of the editor and illustrator.