I was contacted by my editor that my piece lacks "picturing" for lack of a better word. I don't describe the backgrounds of what my character is at. Could someone give me an idea of what the room of the Amulet and the general area it is located looks like? Like what's the landscape? Does it look like a fortress? How does it look outside the room the Amulet is?

Do I even need to worry about it or should it be common knowledge by the 1st chapter?

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I know I describe it as a large room, stone paneled walls, arcane sigils covering everything, with a bismuth colored pedestal in the center with a glass case on top.

But that can easily change, not only from character perspective to character perspective, but as the security measures are upgraded, changed up, etc. They may even have different rooms so Nopony can predict the measures in place.

The first chapter is currently going to be the Cadance chapter, and I intentionally spent some time describing the room the Amulet will show up in. Details subject to change, ofc.

Generally, having an establishing shot is important for writing, because it helps the audience to quickly get a sense of the scene. But unless there is some detail that is important to your chapter, people should be familiar with the major details of the room by the time we get to your chapter.