Board Thread:Questions and Answers/@comment-16461120-20151130214050/@comment-61022-20151201163442

Technically speaking, it would be his first appearance. Often we make a distinction of when a character doesn't fully appear or is mentioned. It's not done here so often, but it's often the case on the handbooks (which is the model we should be following) for example, all handbook entries on Apocalypse specify that he was seen in shadow in and makes his full appearance in.

I would create the page and use the Mockingbird issue as the first appearance but before the issue (in parenthesis) identify "in photo". That way when he makes his first full appearance someone can add that underneath to the appearance of his photo. Hope that helps.