What's so beautiful about the decoration style of the old factory building?
See what your factory is used for, whether it is an office or a staff dormitory, or production and processing, and what it processes. Choose the decoration style as needed. If you want to work and have high aesthetic requirements, you can decorate the countryside, maybe the old color will do. If it is used for production and processing, just clean it. If high cleanliness is required, it must be a dust-free workshop.