Black lamp shade is a great way to introduce subtlety when you do not want the light to overcome your room. Black shades bring in an ambience of muted tone without affecting the harmony of the exisiting decor in your space. Black, contrary to the popular belief, is a good way to usher in a decor style that is one of a kind and a reflection of a bold design statement.
Black lamp shade also allows you to bring in a daring contrast to the neutral and sober hues of furnishings and other decor elements you may have in the room.
Depending on the choice of fabric used, the shade can diffuse different levels of light through it. A thick and opaque fabric can suppress almost all the light through it and so the diffusion of light will only be through the top and bottom of the shade. We in Woodooz Home Decor use fine quality cotton fabric for our black shades which allows for certain amount of light to pass through it, though it may be about 30 to 40% lesser than the lighter hued ones.
If you do not want to draw much attention to the lamp, if you do not want too much light in the room, if you love the subdued and muted ambiance that is just perfect for low light activities like quiet dinners or movie nights, black is certainly your color.
If you are still not sure, check out this post by Woodooz Home Decor on why you should never hesitate buying a black lampshade.