Here, I'll show you.
No, you're not mistaken. It's a clothespin, but only on the Ironforge banner.
I checked a few out. Turns out it was the same way no matter where I went on the tournement grounds.
I then flew to Shadowmoon Valley to view the banners there, and , well, no clothespins. What I did find was fringe.
So what is going on with the fringe? Why are they hiding it in Northrend, but not in Outland or Azeroth proper? I am no expert on things Heraldic, but from what little I know ... that means something.
I googled a bit and found nothing of interest. Yes, they spotted it on the PTR discussions over at MMO Champion, but they didn't make the connection between old and new and thus missed the fringe aspect. There was a topic over at the WoW official forums, but it's just a mention (I had to look at the cached version).