Here is a direct quote from Brom:Wasn't Dark Sun written as Brom's work arrived across the TSR desks? I feel like I read that they built a setting around his art. 4e probably had the benefit of being developed with plenty of lead time and around solid rules.
"I pretty much designed the look and feel of the Dark Sun campaign. I was doing paintings before they were even writing about the setting. I'd do a painting or a sketch, and the designers wrote those characters and ideas into the story. I was very involved in the development process. I've been fortunate to be involved in the development end of a lot of projects I've worked on, from role-playing games to computer games."