I love gold. In any context really, but especially in home furnishings. The great news for me is that brass came back! Just in time to be relatively mainstream when we bought our house. But when we re-did our bathroom, I came to the sad realization that anything brass is expensive. And often hard to find. That's okay, though, because mixing metal finishes can work really well and will probably look better than if you try really hard to match everything in brass. I see it like mixing jewelry, like a yellow and white gold ring combo!
Even if you have no budget, it's not very realistic to do a whole kitchen in all brass with no silver. With stainless steel appliances, small countertop appliances, even hinges and screws that show - you're bound to have something silver. A bathroom would be easier, but still a challenge.
You may not be able to find exactly what you want in brass, either, because the options are a lot more limited. If it's 95% the same finish with 5% something else, it's going to look like you tried really hard and fell short. Better to intentionally mix your favorite finishes. In the example above, the acrylic towel rod helps the silver toilet handle look less out of place.
I like the ratio of finishes in the photo above. I think brass feels like the dominant finish, but the stainless steel on large surfaces like the range hood and microwave balance it out.
I love the kitchen shown above and below (same room). I like the brass trim incorporated on the range hood and especially the refrigerator/freezer, because when you can layer two finishes right on top of each other like this, it's an almost foolproof way to make the mixing work.
I'm focusing on brass because I love gold, but for a farmhouse or old-world style, you could mix copper with brushed nickel, as shown above.
In the two photos above, brass is only used one place - on the hood/oven in the first photo and in the pendant lights in the second. Mixing in a third finish (black in both) makes the brass look less random.
I would have done brass hardware on the cabinetry in the kitchen above to break up all the wood and bring in a little more gold, but the light fixture still works with the metallic tray.
Don't think you have to stick with all matte or all shiny finishes, either. Brushed nickel and polished chrome are used together all the time. You can use polished chrome with a matte gold, too. Caitlin Wilson has some great tips on mixing textures and finishes as shown above and on her blog here.
If you need one more small place to add a touch of a finish, try finding a metal wall plate as shown above!
This bath above is the only all-brass room I've come across (and the rest of it is, too). If you can do it, I say do it! It would be a lot harder to stay consistent in a kitchen, and might be a little much in a larger space. I didn't post any photos of all-silver (nickel, chrome, stainless steel) finishes because until a few years ago, that was every other kitchen out there. Now that there are so many more options, this tends to look blah/builder-grade to me. If you don't like brass, try mixing in acrylic, (can't go wrong) and maybe black!