OneDrive or other cloud solutions sync your Camera Roll. That’s great but how about other folders such as WhatsApp photos or Saved Pictures? Connecting the USB cable and using Photos application to import photos may help but it wasn’t the case for me because of the partially broken USB port on my phone.
After spending sometime searching for an app, I found this one, File Manager, to transfer the folders I select to a cloud solution such as Box, Google Drive or DropBox (Please note that I’m not affiliated with the creator of this app). Trial version will probably do the job.