When scanning old photos, I used to store the picture as black and white, in order to save digital storage space. It is better to start with full color settings, even though it is a black and white original photo or document. In Photoshop and similar software, you can easily remove the yellowing of the picture. This may turn a faded looking picture into a fresh, crisp and vibrant picture. If all you have is black and white data, this cannot be done.
While keeping the original scan for archive, I usually make copies and crop the picture for display to bring out the important features. Many times this allows me to see faces that I could not make out on the original picture. With cropping and enlargement, group pictures can be turned into a series of individual portraits, useful when no other picture exists for that person.