If you choose to see your hard drives on your desktop, what happens with your time machine backup drive icon while a backup is in progress? Does any indicator appears? Are there photos/videos somewhere?
Nothing happens to the icon itself on your Desktop while a backup is taking place. To see whether a backup is in progress, make sure the Time Machine icon is showing in the menu bar, and if a backup is being performed, it will be rotating counter-clockwise. You can also check in Time Machine preferences if you choose not to show the indicator on the menu bar.