Tracks Blizzard employees across various accounts.
[NITPICK] The HOTS Brawl webpage still lists gold and a profile picture as brawl rewards, and in the latest "Next week's brawl" post, it links to the page. It is probably time for Blizz to update the page with the current rewards and such if they are going to link to it in new articles.
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BlizzTravis
Thanks for pointing that out. We'll get that updated.
BlizzTravis
We considered them achievement portraits, similar to the ones you'd get for completing certain events or getting a set of heroes to a particular level. We didn't put any achievement portraits into loot chests so as to not devalue them.