I don't have any better advice on the mouths than what Syn gave you, but I can help with something else. I noticed you're using an oval for the egg shape, but eggs tend to be a bit wider at one end than on the other...
Here's a template shape for an egg you can use if you want: http://i41.tinypic.com/v4tirt.png (Public Domain Image... cause I made it and say so.)
You'll notice the widest part is about two-thirds of the way down the egg, not in the center. Even being all black with no shading you can see it's an egg as opposed to a ball, or oval. All you have to do next is color and shade over it!
Comments
Here's a template shape for an egg you can use if you want:
http://i41.tinypic.com/v4tirt.png (Public Domain Image... cause I made it and say so.)
You'll notice the widest part is about two-thirds of the way down the egg, not in the center. Even being all black with no shading you can see it's an egg as opposed to a ball, or oval. All you have to do next is color and shade over it!
I hope this helps!
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Edit: Another good image search reference for mouths is "Drawing Mouths"... I got a lot of good hits there. ( http://images.google.com/images?q=drawing+mouths )