Photos are visible by default but they can be hidden using the Hide Photos command. You can display the hidden photos again using the Show Photos command of the View menu.
Select the Show command from the View menu by clicking on it.
Then select Show Photos from the Show sub-menu.
This will display all the photos in the floor plan again.
Note: When plans are emailed, all objects will be displayed when the recipient opens the plan even if the object type has been set to Hide.