For formal photos, the background should always be plain. If there is too much shadow in the photo or an uneven background, it will not look right. When working with professional headshots even small adjustments to the angle or pose can make all the difference. A slight tilt of the chin or softening of harsh light makes the photo more natural, while still meeting the requirements. Blurring the background also helps, but it is difficult - too much work, and it may not look document-appropriate.