When filing a copyright application
 

How many pictures do you need to include? It says "Deposit one complete copy." I am assuming that means one picture? Would that be a safe assumption?

If you have only one picture, then deposit one picture.

If you have 120 pictures, then give them one copy of each picture for a total of 120 pictures.

You need one copyright applcation for each picture. Period. It does get rather pricy. Make sure you have everything else in order as well to releases, creation, photographer or artist or it still may not hold water.