Kitty - if you have a scanner, which I assume you do, there was probably software included with it, for manipulation of images as has already been stated by several others above. I've owned several scanners that all came with iPhoto Express software that I like using. You can "spray" a mist over the face, add a circle or other shape of a specific color over the area to be masked, distort the face with swirl effects etc. or you can do what has already been suggested by others here.
If you are preparing the photos for presentation yourself, look around the page where you are doing that, for something to adjust the image you are working with and are about to save (probably as jpeg). e.g. adjust=(crop, lighting, color changes), enhance =(add text, paint over face, add effects, frames etc.)
Do whatever you are going to do to it but make sure to save it with another name so you will always retain your original image e.g. save the changes to image1 as image1e etc. (e=enhanced) and then if you do another version save it as image1e2 and so on.
I agree that it is displeasing when the head is simply lopped off. I prefer to see the hair color and style and also to be able to see the mouth, as I find that quite often shows a lot about the personality.