Underwaves please help me

Yeah um, you have to dive in the code

Select your achievement, click "edit code", and go in the .json file

And the code inside should look like this:

{
  "display": {
    "background": "minecraft:textures/blocks/stone.png",
    "icon": {
      "item": "mineral_galore:cnsword"
    },
    "title": {
      "translate": "advancements.layer1root.title"
    },
    "description": {
      "translate": "advancements.layer1root.descr"
    },
    "frame": "task"
  },
  "criteria": {
    "layer1root": {
      "trigger": "layer1root"
    }
  }
}

Just look at the "background" line and edit the value to "<mod ID>:<texture file path>/<texture name>.png"

Example if I want my achievement have the Blue Spinel Ore texture ("snbore.png") :

"background": "mineral_galore:textures/blocks/snbore.png"

And don't forget to lock the achievement code or else it'll return to plain stone each time you try to edit it.

Datsol