A decorator is a person whose job involves decorating rooms — fixing them up, painting, arranging furniture, and so on. Your uncle might hire a decorator to help him furnish his brand new, fancy vacation home.
You can also call a decorator a designer or an interior designer. Skilled decorators are particularly good at combining colors, fabrics, rugs, and furniture styles to make a good-looking space. Even if you're not a professional decorator, you could offer to help a friend decorate her apartment, painting her walls bright orange and sewing fuzzy green pillows for her sofa. Decorator comes from the Latin word decorare, "to adorn, embellish, or beautify."