As an administrator go to Settings --> Webcam to select Off, Optional, or Required for each employee.
For an employee or manager having their picture taken:
The webcam feature is a permission based system on a per browser basis. Each time a user logs in the browser looks for a cookie, either allowing access or denying access (or asking for it each time).
If you are currently having photos taken per punch, and the employee is not clicking on "accept," that means that a cookie is set to always allow photos.
Simply reset your cookies on your browser and restart the browser. On the next login you will be prompted to accept or deny. You will have a drop down option to always deny or always accept. Make sure to select "always deny." After that point you will never be prompted and a photo will never be taken.
Keep in mind that if you reset cookies that it will again prompt you for permission.