Uncanny Valley Features

I'm trying to think up a character design for the villain of my story, "Magnum Opus"; I want him to have a very angelic but "alien" like feel to his appearence. Along with any input you might have for my design, what do you think are the most prominent traits of a character that evokes the uncanny valley? Is it their eyes or body design?

Eyes are a biggie, yes. I saw a picture a few days ago of an angelic child that was almost photorealistic, except that the eyes were a little bit too big. The effect was scarier than if it had been more sketchy or cartoony.

Perhaps body proportions, as well - like arms and legs being just too long to be noticeable.

I've also noticed that a very angular and rounded face with gaunt cheeks tends to evoke uncanny valley as well; I think it's because it makes the face resemble a skull.

How can you have a face that is angular yet rounded?

That's what's so uncanny about it.

Make characters refrence how strangely attractive they are, to a point that's almost creepy. You say they should be angelic yet alien, yes? Humans typically find symmetry attractive, but there's a point when things get too symmetrical,◊ to the point of being disturbing. That's where Uncanny Valley comes in. They should be attractive on some level, but creepy on another, like one of those pictures that are two things, depending on how you look at it.

More specfically, big, blank eyes are good. Try to have their eyes open (completely open, no half-shut lids) at all times- the less they blink, the better. Also, perhaps make note of how the motion of their mouth doesn't seem to fit their eyes.

Also, refrence pictures that creep you out, and try to figure out why they creep you out. Why does this look uncanny, even though it's very well done? Is it her eyes? Her expression? Her skin?

Slightly misplaced features, especially in the vertical direction: Eyes too high on the head, nose too long, etc.

Oversized pupils, when not paired with oversized eyes.

Long neck.

Excessively long, skinny fingers. Actually, long, skinny anything.

Skin tone too pale and especially too gray.

I've kinda decided on a design for my villain; he's very fair-skinned with curly but elegant red hair (you can look here for his hair style: http://browse.deviantart.com/?qh=&section=&q=Male+Manga+Hair+Styles#/d1344ui (second row from the top, farthest on the right)), gold-amber colored eyes and a thin but lean physique. He sort of has the typical red-head complexion, but the Uncanny Valley comes in the fact that he has no freckles, and his eyes are much bigger than the narrow ones a villain typically has. Am I on the right track here?

There's a few other things you could possibly play around with.

Human skin is not actually smooth - there are wrinkles, body hair, various minor shifts in color etc. Now, however, you have what is essentially an alien being using A Form You Are Comfortable With. A perfectly smooth skin with uniform complexion all over - particularly if it's unnaturaly pale or outright grey - screams Uncanny Valley.

Another thing you could try is absence of body language and non-verbal cues we'd expect from a human, possibly coupled with unnaturally fluid movement.

Uncanny Vally's pretty hard to describe. The whole idea is that something is almost human, but not quite, and that slight difference makes it seem wrong in some way. It's hard to explicitly show, but you should describe the chracter in moving in a way that seems off, and other characters finding something about his appearance unsettling, but not being able to tell what exactly it is at first fight.