Is it possible to recover deleted photos from iCloud?

See the following from If you're missing photos or videos in the Photos app - Apple Support

On iCloud.com

1. Go to iCloud.com, then sign in to your Apple Account.
2. Tap or click Photos.
3. Select Recently Deleted in the sidebar. If you don’t see the sidebar, tap or click the Show Sidebar button in the upper-left corner.

4. Select a photo, then tap or click Recover.

iCloud Photos and iCloud Backup are two different services. If you have iCloud Photos (a syncing service) turned on in a device, then the photos will not also be included in an iCloud Backup of that device. See the following for more information about each.

If you have iCloud Photos turned on, the photos on the device are the same as on iCloud, with the possible exception that some of them may be space-saving optimized versions if you have that option turned on. You view them in the Photos app on an iOS device or Mac. You can also login to icloud.com and go to the Photos app there. The following Apple article has information about iCloud Photos: Set up and use iCloud Photos - Apple Support

If you didn't have iCloud Photos turned on but do have an iCloud backup, you can restore the entire phone (not just the photos) from iCloud but you cannot otherwise view the contents of the backup. The following Apple article has information about backup: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support