Extra Thoughts

 If there are missing areas of a photo you may beable to get them back. Sometimes easily, sometimes it may take a bit of ingenuity on your part as well.
I find usually a missing eye can be selected & copied from the other opposite eye. It needs to be done as a layer though, as it will need to be flipped. Remember faces are not symetrical. You can get away with it more on other parts of the body as long as you have people standing/sitting straight on.
Buttons, medals etc can be done with the clone brush if there are some already in the photo.
Sometimes one side of a body, usually only a small area (maybe a neck, collar and arm including part of the chest can be selected then copied as a new layer, flipped and put in the place where the other side should be. You can also do this with legs. Before merging down erase any extra away of the new layer as possible (If your new layer is selected only it will be affected).
Where appropriate I have even used photos from the net to fill in missing parts and also the blur tool and smudge. 
If you intend to use thes photos online only use creative commons or public domain photos though.
Whenever making a selection to copy an area, always feather it at least by 3 pixels (more depending on the size) to give it a smooth merge.  You still may need to use the heal tool to soften the joins.