iCloud is like synchronisation service, not like typical backup service. You cannot select certain photos not to be uploaded.
You can save those photos to iCloud Drive and your hard drive tho.
Delete the photos in question from the Photos app... put them somewhere else - local storage, drop box, iCloud, etc... but that's how Apple's Photos sync works... if it's in the Photos library, it gets uploaded everywhere... if you delete it, it goes away everywhere.