I recommend just searching “courtroom” into Google Images. You will be presented with a handful of concepts that you can use for your build. They tend to be fairly wooden and traditionally themed.
Going off what has been said above; when creating sorting items it’s always good to use images for getting those ideas for a courtroom. It’s always good to use reference images that way it’ll show you what details to implement and things it features - it’ll act as a sort of guide, when recreating a courtroom. You could even view ones around your specific location to get the design and layout correct.
The decorations should be based on the style and theme you’re going for most courtrooms normally just feature chandeliers and statues attached to the wall structure. The material choice could be thrown in sorting parts of the buildings; courtrooms kind of have a wooden light or dark texture, the material scheme could be related to the style or theme your courtroom is set in.
Finding materials, color pallets or sorting decorations, or a layout. Try gathering a few reference images to get some general ideas on what objects are needed, and what makes a courtroom unique in a kind of way.