Because almost any object can be made into a light fixture or lamp, decorative themes can be expressed through light fixtures in innumerable ways. A good fixture will cover up any defects in your space. You can draw the eye to a pretty fixture when your budget disallows you from replacing your old couch with the shiny new one you want. Expensive fixtures will make a modest home look high-rent, while cheap looking fixtures will attract negative attention in an otherwise expensive dwelling. So, it's not just about what type of bulb is in there, or how bright it is, or where the fixture is placed in a room! It's very important that you use a light fixture that is in keeping with your period or style of architecture, the mood you want to create, the price range of your other furniture and finishes, and the themes you have chosen.
Left: I found this light fixture at the Chelsea Market. Even though the high ceilings, large spaces and raw walls of the market are very much industrial, this Deco fixture works because it evokes a sense of style and sophistication that their target shoppers probably identify with. Also, it's large, about 26" high by 10" wide, so it is proportionate to the space. Pairing industrial with ornate early 20th century is a thing, by the way, and it is not going away.
Below: These green lights adorn the entrance to a police building on Grand Ave in Prospect Heights. These lights are original to the building (unusual in NYC!), they are inviting, yet they command respect and attention. I've seen a few precincts in Brooklyn with these antique green lights. I guess they're perfect for connoting a place of importance. Side note: I've noticed that NYC doesn't have a lot of its original outdoor light fixtures, whereas Boston does, by comparison. I'm sure it's something about which Ken Burns would have some handy information.
Right: Here's a cool little fixture in a trendy restaurant on Washington Avenue near the Brooklyn Museum. It looks custom made to me, like a fabricator took some chicken wire glass, cut it up into a rectangle and bolted it to a metal plate with a socket in it. I love it. It's modern industrial but it's reminiscent of the 1920's. Or it's maybe even from the 1920's. Either way, it makes me think of a farm, and it's perfect for a restaurant that caters to the hip crowd who want to eat from farm to table. It's small, but that's okay, because there was a series of three of them, located above the table areas. Appropriate.
Above: This gem of a light fixture is mounted above a bike shop on Conselyea St. in Williamsburg Brooklyn. It's a light fixture made from a tricycle, mounted above a motorcycle shop. Need I say more. I want it, everywhere.
So! There you have some examples of cool light fixtures that are appropriate for their environs. I hope they inspire you like they inspire me. Remember: your light fixtures can make or break your space!