As part of a business photo engagement, here is an example of how I created a group photo for a financial advisory group. First, I created a business portrait, full length, of each financial advisor taken against a white background. Following the shooting, each image was retouched and masked or removed from the background.
During the photo shoot, I shot several background shots of the firm's offices and processed them as HDR images. I placed myself in each scene for scale (I'm 5'6").
All 9 individuals were roughly placed in the scene to approximate, but not exact scale.
Several steps were used to scale all of the people (bringing them slightly closer to the camera) as well as scale them to each other. Shadowing and edge blurring were added to each person. In addition, the background was darkened at the bottom and blurred as if the scene was taken with the camera wide open. Finally, the tone and brightness of the group was adjusted to match the tone and brightness of the background.