Although I never had more than 3 devices connected to Dropbox at sane time; but Dropbox Camera Upload used to rename all the photos to time & date it uploaded; I will have same photo with it's correct time n date took as name in my phone, & it's copy with a different name in Dropbox. I used other sync apps to connect & sync my Camera folder to Dropbox, like FolderSyncPro. Apps like that can connect from any number of devices.