[Runscott]

As the result of an off-line conversation, I'll add the following about print restoration:

For torn photos I normally try to push the tear back in place, then use surgical tape to repair from the back (never the front). If the tear is straight enough, I cut the surgical tape thinner, so that it is an unobtrusive as possible.

For the damaged parts of the image that remain, you can use gauche paint. Gauce was the choice of restorers in the past because it does not soak into the paper;i.e-what you see when you apply it is what you get. As a result of its past use, you can generally find shades that would be used in photos in art supply stores. You might find gauche in Michael's or similar, but it probably won't be the correct grayish shade (or browns for some albumens).

I would first find a photo of similar gray shades to your repair area, tear it and practice. If it's a valuable photo, practice a lot, until you feel like you can do it easily.