That's a good technique. And in general that's what I try to do: work it in so that the reader gets an idea of the physical description without needing me to say, "This character is thin with brown hair and green eyes." Although I don't think I've used the "dark setting=dark physique" technique at all. I'll have to keep that one in mind.

I'm also don't hang on to visuals when I'm reading. If it's important that a character have green eyes for a huge plot revelation later on . . . I'm going to totally miss that. Because the writer may mention green eyes repeatedly, but a paragraph later I'm not going to remember that. Because I'll already have a picture in my head and I'm happy with that, and in most books my picture works just fine, thank you. *grin*