[James]

It seems like the two most likely speculations for Gothmog's race are human and orc. So I'm thinking that the cause for his appearance in the movie was intented to be a cross between these two. He's pink and deformed, so I almost think the idea for the movie appearance might have been that he was a man distorted into a monster.

Many thanks for this link. I'd found an encyclopedia online back when Fellowship came out, but I'd closed it when it spoiled that Gandalf returns, and could never find it again. This site blows that one out of the water.