Here's a post that might help you - https://www.ehow.com/info_8613461_can-podge-wall-printed-photos.html
Sounds like a really great idea Joyce! I do have a concern however! What will you do if you ever decide you don't want the photos on your wall any more? It would be hard to remove them as you would have to try and sand them off and it may not be attractive to paint over them. I could see mounting a 4 x 8 sheet of plywood (or more) to your wall and use that as a base to mount your photos. You would have a large area to display the pictures plus you could just unscrew it if you ever wanted a change and there would be little damage to the wall underneath.
I would be hesitant to use original pictures, but, I have put them on a steamer trunk and crafts without a problem when I used copies.
Glue, wallpaper roller and patience.
Sensible advice from Gk.