One of the first concerns is the degree of consistency of all of the head shots or portraits for the bios. Some firms want each one to be as much alike as possible. They want the same shade background, lighting, cropping, expression, etc. While some branding or consistency is good, one thing to keep in mind is that there is not one system that makes everyone look their best. Just as there is not one suit the same size, color, style for both men and women that looks good on all, photography is the same. Obviously balance is needed. Below I have some suggestions that might help.
Lighting: Adjusting the lighting (as many as four different ones in different positions) can help a heavy person look thinner, really thin person look healthier, or accent beautiful hair and bring out the person’s best feature. A one light fits all eliminates the ability to bring out a person’s best features and decrease the worst.
Background: I would recommend a neutral background such as grey that can be lighter or darker depending on the person. For example light hair looks better on a dark background and dark hair looks better on a light background. Brighter or more textured backgrounds can look very nice or really pop, but might be harder to match in the future.
Pose: Since people have a good side and a bad side as well as long necks, double chins, etc. The pose should be adjusted accordingly. Sometime a person looks better when they lean into the camera. This can reduce a double chin or long neck. Sitting and using a posing table allows more adjustment than standing.
Expression: A company might want every to have big smiles. We all love smiles and people in real life normally look best when they smile. However in pictures, some people look silly when they smile for the camera. It could be the teeth, lips, or just a really big mouth. I had a distinguished attorney smile and it was so big he looked like the joker from Batman. A more serious expression was better and he looked great. Each person is unique and a good photographer will try various expressions (theirs, not his).
Cropping: Cropping is very important with professional head shots. If too much body shows, a person can look really huge. However if the cropping is too close, the person is really “in your face” and that is kind of awkward. For portraits of one person or a head shot, I recommend a cropping proportion of about 5x7 vertical. The head takes up about 50% of the image and not too much body shows. The eyes are located at the ideal 1/3 down from the top. This way there is not too much space at the top where the person would look really short. In this case the personality in their face and eyes are the important thing. The proportions change for half length, full length or when you have more than one person.
The above would give consistency while allowing the photographer to make the person look their very best.