Has Overwatch Been Teasing Its Wrecking Ball Character Since Beta?

Blizzard revealed Overwatch's newest hero, Wrecking Ball last week and, to most people's surprise, he was a hamster called Hammond driving a mech. But that surprise might have been lessened if we'd spotted a possible clue that's been visible since the earliest public versions of the game.
As pointed out on ObscureWatch, a single billboard visible on the Lijiang Tower map holds a weirdly specific clue. Originally, interest was focused on the billboard's character art. It's unique in the game, and