As for writing it yourself, care to talk about the price of the developer account, the approval process, the risk of getting banned, the ever changing API surface, the time you use for all of this, etc. etc.? You are NOT the owner of anything in the "metaverse". You are just allowed the privilege of playing in the platform owners sandbox as long as you pay. When the platform owner will decide it is profitable to exploit users ability to set wallpapers there is nothing you as a user or as a developer on top of the platform will be able to do to counter that.
Here, read this (1) and watch this (2) and tell me you feel confident the same will not happen to any "metaverse".
(1) https://pluralistic.net/2023/01/21/potemkin-ai/#hey-guys