To me the most defining thing about scorpio eyes are not the eyes themselves but the fact that they don't mind staring at you, and they don't back down when you hold their gaze.
So staring contests with Scorpio-types are always fun
...unless they are pissed at you. I grew up with a mother who has a scorpio asc. and a stepfather who has a scorpio sun and mars square pluto (forgot the rest). they both scared sometimes, but my stepfather especially could send me hiding under the bed with a glance of those needlepoint sharp, blue eyes.
Here are four whom I know (minus my parents since I'd have to drag out actual photographs). What do you think? "Scorp eyes?"
Top: Scorp Sun conjunct Saturn, Aq. Mars square Scorp Pluto, Asc unknown
2nd: Scorp Venus, Merc conj Pluto in Scorp, Aq. Mars square Scorp Pluto, Asc in Cancer
3rd: Merc in Scorp, Venus conj Pluto in Scorp, Asc. Unknown. Also though, he has Sun conj. Uranus/Saturn
Last: Neptune conj Scorp Asc, Merc/Venus/Pluto conj.
These look like Scorpio eyes (she can send shivers down your spine.. silent, smoldering and piercing looks she gives on occasion), except she has virtually no scorpio or pluto in her chart, except for a mercury trine pluto, although I don't have her birth time so I don't know her ascendant or moon. I'd guess they must be Scorpionic, its too strong an impression.
Sorta what I'm getting from the people I know, is that certain other aspects besides the scorpio ones can enhance the scorpio traits enough to come through in certain ways. I see a prominence of mercury in the stereotypical scorp eyed people I know (in a side note, from comparisons I've done I've also seen Mercury paired up with Mars with strong Aquarius influences to show up in people with distinctive voices), and Uranus or Aquarius. I know other Scorpios that don't have that look about them, too. What do you think?
I'd guess that Uranus would also have more of a hand in taboo stuff that Pluto often gets a rap for. When these two planets team up though all hell breaks loose.