I don't understand all of these stipulations on first appearances. It doesn't matter if the character is in the foreground or background, whether you see his face or not, whether the character speaks or not. (Does the character appear on the cover? Makes not one iota of difference.) If a character appears in any way, shape, or form in an issue, that is his first appearance ... period.
You can use whatever adjective you want (cameo, full, etc...), or collectors may deem another issue more desirable, or the market may deem another issue more valuable, but if the artist drew him into the story, it's his first appearance.