Watched a lot of YT videos on blender shaders. Recommend 'Top six blender nodes to make any material'. Started using color ramps everywhere to control how different nodes are mixed and to adjust color values and contrast.
It seems that with procedural shaders, simpler is better, you can always add detail to a specific model, but putting detail into general-purpose textures starts to look ugly.
Made a couple of shaders for this 'room' and played around with lighting:
