I vote for images that are striking, aesthetically appealing, original, and done with some skill.

Many of the images submitted to the Halloween contest look very amateurish.  Expressionless faces, unnatural poses, clothing that appears immune to gravity, poor lighting.  (And yeah, I know I've committed many of these sins myself over the years. Hey, I'm not a contest winner.)  I tend to skip right over those.

Then there are the renders that are attractive and very professionally done...but so trite in Poserdom that they don't really stand out.  Typically a sexy, barely-dressed witch posed on a DM set.  ;-)  Absolutely nothing against fantasy pinups, it's just that you see it so often here at Rosity, it kinda doesn't register any more.

Typically, I vote for images that are different. I still remember an image from years ago.  I think it won.  It was a farm scene at night.  There was a cart stopped by a field of corn, and drags marks where something had dragged whoever had been in the cart into the corn.  It was just so creepy and mysterious.  So many years of Halloween contests, and probably thousands of images, but that's the one that I always remember.