During the Age of Empires IV: Showcase Recap today, Adam Isgreen made a minor announcement on what the coat of arms and monuments are included with the Digital Deluxe Edition.
The coat of arms will be a customizable graphic in the game outside of a match, in addition to the player portrait, with different colors, symbols and tabards, similar to the customizable coat of arms from the Fan Preview Virtual Village. A few customization options will only be available to those who purchased the Digital Deluxe Edition.
Monuments are cosmetic items which are unlocked during game progression and are featured in the center of your town center building during a match. There will be a special monument only available to those who purchased the Digital Deluxe Edition.
Both the coat of arms and monuments are purely cosmetic items without providing any competitive advantage.