I always wanted to have a levithan blade behind my back and wear a massive bomb behind my back so i can look more like NPCs and enemies in the game. So i think they should add accessories like
Back Levithan Blade
Back Bradish
Recon backpack
Iron Claw backpack
Big Bomb(bomb Warmaster Seerus wears)
Spiral banner
Warden banner
Veteran banner
Darkfang banner
Crimson banner
I also wanted to add knights you see in haven in my guild hall so it doesn't really seem empty when you walk inside and your guildmates arn't around. So i wanted the game masters to add new guild decorations like
Recruit
Wandering Recruit
Soldier
Wandering Soldier
Veteran knight, Female model and Male model
Wandering Veteran knight, Female model and Male model
Spiral Warden
Researcher on computer
Banners: Spiral Banner, Crimson Banner, Jelly Kingdom Banner, Almiran Banner and Owlight Banner
Thanks for reading give me suggestions in the comments
For the guild decorations, I was thinking about this myself not too long ago. Would be able to bring a bit more life to guildhalls.
As for the accessories, no to specific weapons on your back. However an option to have whatever weapons you have equipped show up on your player would be nice somewhere (slot one in hand, slot two at side, slot three on back, slot 4 crossed on back).
The two backpacks are cool ideas too.