[Knight of Gondor]

Sometimes inspiration or visualization can creep into the mind unawares. You begin whistling a tune and think it's not half-bad, until you realize (or someone else points out) that it is this-and-such a song, which you likely heard some time ago (perhaps subconsciously) but forgot the source of.

I looked at the side-by-side comparisons on the site, and I think only a couple of them are legitimate. Many of them are inevitable from the way Tolkien described them. The designs of the Moria door, for example, were put in the book. He can hardly take credit for that. Arwen and Aragorn embracing is not similar at all. There's only so many different ways that two lovers clasping each others' hands can appear, and only so many different ways you can depict a giant elephant.

Some of them are only similar because they depict the same events.

The strongest one, I think, is the one of Aragorn kissing Boromir's brow.