Alright, I guess a lot of people have been asking about eyes, so here I've created something of a tutorial for making eyes. They really aren't that hard, as long as you have certain elements in them (and of course they look both the same).
Here are some differen't heads up close for you to look at, and a transition of a 'naked' mini head to one with eyes. Most prep heads and paper doll heads come with eyes on them already, so all you have to do is edit them to your liking. If you make eyes on say a prep or a paper doll head, you will notice they appear to be looking to the side of yourself. This makes it so the eye closer to you looks larger and you see the whole of it.
The other eye is angled away and the 'nose' partly covers it. As you can see the right end of the smaller eye lines up directly with the close end of the nose. I hope you can see what i'm saying. The pixels of each of them are either right next to each other (lined up of course, not literally) or just one pixel wide.
If you'd like to check your dolls, just draw a line in your painting program next to the side of the smaller eye and draw downwards, and see where it hits the nose (or see if it even does).
The paper doll head (uppermost left head) is the way I always like to do the eyes on my dolls. Its all just a matter of preference. I've shown many different styles of heads, and its all about the style you yourself learn to develope in creating different styles of eyes.
As you can see on this mini head i've shown basic elements on how to make the eyes. After you put in the basic lines of the eye you can create different eyelash effects on them. Also you can notice that the inner edges of the eyes line up directly with the noce. Thats usually the best way to have the eyes and the nose when your making a doll looking straight forward, like this mini is.
Here are some more close-ups of heads and their eye styles:
Like I showed you before, its all about how you like the style of eyes to be. Being these are cartoon dolls, your sort of limited with what you can do, but just zoom up in your paint program close and just experiment with eyes, as with anything else.