Can I have photos on my iCloud but not held on my iPhone? I've just found hundreds of old photos which I am going to scan into my iCloud but I don't want them to be added to my iPhone. Is there anyway I can do this?
If you have a Mac or Windows with iCloud on it, you can have them uploaded to iCloud via iCloud Photo Library.

If you don't want them on your computer then you'll have to upload them via www.icloud.com manually and that way takes a bit of time.

Your best route is via a computer.

Just make sure that you keep iCloud Photo library turned off on your iPhone's iCloud settings.