The original situation sounds not much of a risk, with or without snapshots. Also, If somehow you backup a halfway-saved photo, the next backup will likely get the full photo. Constant changes are harder to deal with, for example virtual machines and databases sometimes requires special tools and methods (e.g. database dumps) to be application-consistent. LVM does crash-consistent. VSS can use application help, if available.
Some Duplicati forum articles on consistency:
Backing up Hyper-V guests / vhdx
Backing Up Server 2012 R@ Access Denied
Linux distro LVM support varies. It adds capabilities and complexity (which some hide until it trips Duplicati).
Basically, I’m just saying that knowing the exact needs is important. Demanding needs are demanding. 