iTunes is an easy to use tool to backup and sync your iPhone with other devices and services. If you're using external folders on a Windows PC to store pictures, you can instead sync your iPhone or iPad from that specific folder using iTunes.
Here's how you can use iTunes to backup photos from PC to iPhone
- Organize your images into folders and subfolders.
- Plug your iPad or iPhone into your Mac or PC.
- Launch iTunes, if it doesn't open automatically.
- Click on the iOS device icon in the top bar, then click the Photos tab.
- Click the checkbox next to Sync Photos.
- Select "Choose folder" from the drop-down menu.
- Click your desired folder.
- Click to sync All folders or Selected folders, and whether or not to include video.
- Click Sync in the bottom right corner.