Yeah I don't really understand what the thesis of this article is. Copyright infringement would apply to any of those images just the same as if you made them yourself.

I don't think it's possible to create an "alien which has acid for blood and a small sharp mouth within a bigger mouth" without anybody seeing a connection to Alien, even if it doesn't look anything like the original.

Your second paragraph may be true, but the mere abstract presence of those features wouldn’t infringe copyright.