Could be in the supporter pack 2, a leveling cosmetic, or some sort of easter egg cosmetic by completing a hidden quest.
These items could range from being able to place a duckie plushie on top of your helmet to being able to change your helmet to a top hat, etc. Most important part is that its goofy and fun for casual players.
For the sake of milsim-ism and competitive integrity an idea could be having setting(s) that turn off cosmetics for the enemy and/or being able to turn off enemy cosmetics