The only new graphics we have high probability to get is a unique model for the Mounted Samurai
—it currently exists as a scenario unit in AoE2, but borrows the Hussar model.
That’s because in the 1551 Sengoku Japan scenario, you play one of six factions, and one of them is sure to be the Takeda clan, who will have this unit as their signature. It would be a little tragic if the Mounted Samurai still don’t get to look like one in its official highlight moment.
As for any other units or heroes: hard to say. Nothing they have shown of the DLC—the menu map screen, the Constantine XI scenario—contains any new models.
Other than adding voice acting, the Constantine XI story slides are completely unchanged from the Mod Workshop version, reusing old slide art.
In general, the prospects do not bode well for them spending money to make new art for this. I hope I’m wrong.
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Relevant to the cheapness of the DLC: