Ah, headshots, an art unto themselves.
Your examples are very good (I especially like the 2nd one) you are on the right track and haven't made the mistake many make with headshots. Headshots aren't portraits, they are advertising tools. They are used by directories (stage or screen) to determine who they are going to hire, nothing more, nothing less. Many actors hate their headshots because they are so plain looking but that's what they are supposed to be.
The headshot should show what the actor looks like (i.e. not a fake looking glamour shot) and demonstrate how the actor can connect with the audience/camera. For this reason the eyes are the #1 most important part of the shot. Keep the background simple (preferably completely blurred), keep the clothing simple. Dont detract from the face.
If someone looks at the photo and says "thats a great photo" it's probably not a great headshot, the headshot is all about the actor's face, not the photographic skill. This is why many new actors balk at what a good headshot costs, it seems so plain for what you pay, but that's the idea.
Try taking some more shots and don't crop them so tightly. Include from the mid chest to the top of the head. You are on the right track with the poses and clothing. Dont take them straight on or they'll look like bad school photos. If the body is straight on, the head needs to be turned, If the head is straight on then turn the body a bit. Be careful with tilting the head, it can look cheesy (think Glamour Shots, or bad school photos).
Generally actors have a couple of poses expressing different moods and select accordingly when submitting their headshots for consideration (serious, happy, intense, etc.) This is less of a problem for kids and as long as they dont end up looking too syrupy and/or pixish, a nice slight smile will be fine (intense expressions on children can look pretty creepy and there aren't many roles for creepy children). The expression should make them look like a professional. Think "been there, done that".
The sad fact of headshots is that they are a necessary evil. A good headshot wont necessarily get the actor work but a bad one will prevent the actor from getting work.
You might also consider adding a white boarder with the actor's name. This makes it easier for directors to keep things straight if the resume gets detached from the headshot.
Also, headshots are always taken in a portrait orientation, not landscape.
Here's some examples of pro work:
http://studiomark.com/headshots.html
Another good resource is:
http://www.headshots101.com
