I have no idea why they’re referring to these as "banners," but some of these designs are not half bad. Actually, they are pretty good:

http://www.pittsburghmagazine.com/Best-of-the-Burgh-Blogs/The-412/April-2014/Heres-Your-Obligatory-Game-of-Thrones-Inspired-House-Penguin-Sigil/

Heraldically, I think the Washington Capitals (the one with the eagle, I’m guessing), the Islanders (the anchor one), and the CO Avalanche (blue mountains, on a purple field, etc.) shields are the best. The Rangers one works well too, but theirs was already vaguely heraldic to begin with.

I think they’re banners because they’re envisioned to be made of cloth and hang from the rafters

Certainly not "perfect" heraldry in many cases, but pretty sweet from the perspective of someone who is a hockey, heraldry, and G.O.T. geek like myself