Not sure if you are aware but there is a difference between iCloud Backup and iCloud Photos. If iCloud Photos is turned on in a device, the photos are viewable on both the device itself and by using a computer internet browser and logging into iCloud.com and going to the Photos app there. More information: Set up and use iCloud Photos - Apple Support
If you don't have iCloud Photos turned on but do an iCloud Backup, the photos would be included in the backup but you cannot view the contents of a backup; you can only use it to do a full restore or to set up a new device. See: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support