Well, I'm not sure what your definition of "evil looking" actually is, but if you're creating a sim that you intend to be an evil vampire, and you're going for a sinister look, I have some ideas.
- When your making their eye color initially, make it a very dark red. But whichever color you decide to go with, you want it dark to start with because after they become a vampire, the "glow" will lighten the color up quite a bit.
- Their skin tone will get a sickly sheen after they turn, so the lighter you make their original skin tone, the more obvious it will be.
- There are also some arched eyebrows that can give your sim's a perpetually devious look. Select those, and then adjust the orientation of them manually until they're sinister enough for you.
- Manually adjust the features of the face, especially the cheekbones and the cheek fullness settings. Try to go for sharper cheekbones and sunken cheeks, and if it's a male, try to square out the jawline a little.
I'm going to give it a try here, and see what I can come up with. Maybe I can whip up a little bit of a tutorial.
Edit: Some marginal success, although it hardly requires a tutorial I guess.
First the male, Barnabas:
I picked the first random male sim I came across. I slimmed him down almost to the minimum, beefed up his muscles and maxed his muscle definition, and made his skin tone as light as possible. From there, aside from eyebrow selection, I raised his cheekbones and made them as sharp as possible, set his cheek fullness to minimum, narrowed his jaw slightly, and rotated the corners of his mouth up a little bit to give him a wicked smirk. I also rotated his eyes so they slanted more towards his nose, set them to maximum depth, and made them a very dark red (they almost looked black in CAS). I also accented his sunken eyes with brown eye shadow, gave him some fine eyeliner and lipstick with the opacity set on about half. I changed his hair color to black, too and changed the highlights and tips to very dark gray.
The female didn't look quite as evil, though, but I give you Celene anyways:
I basically followed the same procedure as above, only not quite as pronounced. I was trying to go for a little more of a subtle evil with her (trying for a less angular Elvira Slayer look), and I don't think I really pulled it off. The only difference was that I made her eyes yellow: I went into the color wheel, set it to almost straight yellow, then slid the tone bar to darken it greatly. Her eyes looked brown in CAS. And since I have a thing for redheads...that was a must as well lol.
But while vamping her out, I did catch something that I thought was quite funny:
Elvira's like "Um...excuse me?"
