Doorknobs should match giving it a theme that runs thru the entire house however light fixture and oter hardware you can vary according to the decor of the room. It will also be less boring..

Nope! In a bathroom, I would have all the finishes in the same color family, by which I mean that I would happily mix chrome with brushed nickel or pewter, ad long as it's basically a silver tone. In the kitchen, I might have a chrome faucet, brushed nickel cabinet hardware and island pendants, while nearby having an iron or oil rubbed bronze chandelier over the kitchen table.

Now, let's talk about the dining room, and we'll make it simple. Use whatever color of metal you want.

But for your door hardware throughout the house, I would select one metal, and right now I'd make it brushed nickel, or for a more contemporary look, chrome.

You may have noticed, or not, that I did not mention brass. I hear mutterings about its comeback, but am not yet a believer.
Carolyn Albert-Kincl, ASID

I don't think brass is in our near future either, lol