You may choose to let your customers see files names for their images in proofing events. By default file names are not displayed.
To turn on the file names, first open the event from the proofing control panel and click on the gear (top right corner).
Toward the bottom of the page there is a section for Display File Names. Select Yes, and save changes.
Now the file names will appear when people mouse over an image in the grid view.
In addition, the file names display in the large view of images in the icon bar.