I have a card, creature Nekrataal, which shows the logo from the Visions set, but has a gold border and signature.

The back is different; it shows "Magic the Gathering DCI 1997 World Championship Seattle August 1997" I can't find this as a block or set on the site.

How would I go about listing the card on the site?

Championship decks are not yet a supported. as a workaround, I believe that most people would label it as visions, and add the promo flag