We've datamined the models for the Stormrider's Stormhammers, which match the War Within preorder transmog perfectly.
Arsenal: Stormrider's Stormhammers showed up in the data last month with encrypted models, but the name lent itself to 11.0 story speculation--which proved to be correct as it shares a name and color scheme with the preorder rewards.
Post-BlizzCon, the models have been decrypted, so we can see what they look like, as well as unused color variations.
The Regal Stormhammer matches the base Stormrider's Attire set, available from the Heroic or Epic War Within Preorders.
The Thundering Stormhammer has additional lightning and glowy effects, and matches the upgraded Thundering Stormrider's Attire set, available from completing special Storm Rider Races on your Algarian Stormrider from the Heroic or Epic War Within Preorder.
We've found a bunch of unused recolors, which match the tints for the Algarian Stormrider customization options as well as unused tints for the transmog set.