Some of the coolest stuff on the PTR are the new glyphs. And one of the coolest purely cosmetic glyphs I've run into is the Glyph of the Weaponmaster. In the header image above, you can see me dual-wielding Uroe, Harbinger of Terror and Bo-Ris, Horror in the Night. And yes, they happen to look like the Warglaives of Azzinoth. That's because I have the glaives in my backpack, and so, every time I use Battle or Commanding Shout, I get a ten minute buff called Weaponmaster that picks randomly from every weapon I have in my original backpack, and places that weapon appearance over my currently equipped items.
The buff doesn't care about weapon categories as far as I can tell - two handed weapon models can go over 1h weapons and vice versa. Polearms can become swords or maces or fist weapons. (In fact, it can even put the wrong fist weapon model on a hand, so that it's clearly backwards.) If you switch the weapons out, the effect fades but the buff remains and it can bug out so that you have to clear the buff in order to use the effect again. But it does allow you to basically switch between a variety of weapons in your main bag if you like variety, or it allows you to effectively use legendary weapons in your current transmog look, if you're a warrior.