Would you be willing to accept a PR which determines if a photo exists in the directory before attempting to download it again? This would help those on limited connections as well as reduce API calls as it appears you're having to pass one of the API tokens through to download.

My use case is that I have a public collection named Backgrounds which I add photos to whenever I see a background that I like. I then use Bulksplash to "sync" new photos (but currently it re-downloads them all) to my laptop's wallpaper directory.