What seems to happen with the mat room is that when you first go into it, with a mat pose applied, the node connected to diffuse_color will be called "Color Texture". If you then remove that and add a new image map, it will be called just Image_Map. Add some more and you'll have Image_map_2, etc. You can also see this with trans maps. When you first enter the room, they're called, um, "Transparency_Map" I think, but again if you remove the original and add a new one, it'll become "Image_Map".

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"you are terrifying
and strange and beautiful
something not everyone knows how to love." - Warsan Shire