In issue #52 of the Fantastic Four "world's greatest comic magazine" Jack Kirby and Stan Lee introduce the Black Panther, the first black superhero. This is the famous cover
The cover Kirby prepared initially was rejected. The unused cover has been published, much later, by marvel Comics in the Masterworks series (I believe. I found it on the web)
Note that, unlike the final cover, the mask on the black panther does not cover the whole face.
What it is not widely known is the fact that Jack Kirby prepared a second cover, that was sent unretouched, as many others, to the Italian publisher Editoriale Corno in the '70s.
The above is the cover of I Fantastici Quattro #48. Does it look familiar? Of course it does! It is "almost" the cover published in the US. Almost. Look at the Panther: the Italian publisher decided to color the face in black but the Panther clearly wears the same mask as Kirby's unused cover. And his short mantle is the same too. But wait, it seems the whole figure is taken directly from the first unused cover, flipped and rotated!
To prove it I selected the Panther from the first cover and superimposed, colored in green, to the Italian cover, to prove my point: they are identical.
So, after Kirby prepared this second cover, someone at Marvel decided to cover the face of the Panther. Or maybe Kirby simply forgot that inside the book the Panther's face was completely covered and when he realized that, he changed the cover at the very last minute. Here they are side by side
So, after all, a portion of the first cover prepared by Kirby ended up in the final published version, the third version! :)