Well as @intrepidphotos mentioned, it's usually important to "prove" you are the actual author of the photos instead of picking them off from a photographers site (etc.) and pretending to be you.

You can imagine, you could find someone pick a bunch of your photos from your website and then post them here, pretending to be you. But hopefully you are truly you :)

So cross-linking is usually one method to verify yourself, as mentioned. Not only pointing out Steemit -> Your web page, but also Your web page -> Steemit. That's usually one of the strongest proof, as it can prove you control the website and it's pointing out to your Steemit account.