Yes. You can turn Off the backup option in Dropbox Carousel. To do so, simply tap "Menu" located at the top left corner on the screen to enter your "Settings". Now tap "Backup Options" and the disable "Back Up Photos & Videos" option. This way you can turn off the Backup Option in Dropbox Carousel. If you take photos and videos on your device, you will see those photos in Carousel but those photos will not be backed up to your Dropbox account.