A new video of added weapon models for Legion shows off what appear to be several new looks for Protection Warriors' artifact mainhand weapons as well as some new looks for daggers (not sure if these are Demonology's mainhand weapons or for Rogues - the lock-and-key one looks very Rogue-appropriate, but the patterns - and fel-green tint - on others look very Demonology-appropriate.)
While a lot of the mainhand weapons for the specs whose primary artifact is an off-hand item (which I believe are the two Protections and Demonology - Elemental and Restoration have shields, but it's their mainhand weapons that get the spotlight) have appeared as a single model, this new collection seems to suggest that these were just placeholders.
What's perhaps more exciting is that not only are there going to be unique weapon models to go along with the unique artifact looks, but a lot of them change up the weapon type.
For instance, the baseline Protection Warrior shield goes with a sword, but in the MMO-Champion post, we see a one-handed axe, mace, and flail (guess it's not just for us Crusaders) that all clearly line up with existing looks for the shield. So, for example, if you go with the Deathwing-themed shield, you'll get a nasty-looking Deathwing-themed mace.
Given that we're stuck with our artifact weapons for the whole expansion, I think it's wise that they're opening up a bunch of options for the kinds of weapons we want to use. Weapon type doesn't really have a mechanical meaning other than what's available to your class - Orcs don't have that Axe Specialization passive, so they won't feel forced to take the model with the axe - so there's no reason Blizzard can't unleash all the ideas based on the artifact themes that they can.
And please, please, give me a version of the Ashbringer that's a two-handed mace in the form of a mighty warhammer! There are painfully few good warhammer models, and the last good one was Hammer of the Naaru, from BC. (Actually, scratch that, the Black Hand is pretty good, but not as easy to get, and also not very Paladin-y.)