I just did a Google search for hanging black onion lighting and several came up.

I'd probably need more details (countertop choice, other lighting nearby, shade of grey cabinets, etc) to comment on how it would look.

Don't be afraid to mix metals - it's usually more interesting that way.

I think you could find authentic lanterns in pewter if that's a look you like. Google pewter onion lantern and see what comes up. Here is a beautiful one from the Nauset Lantern shop that comes in various sizes and finishes, including pewter:

New England Copper Works at http://www.necopperworks.com/hanginglantern.html also offers hanging onion lanterns in pewter.

They are expensive, but beautiful!

As far as etiquette, I'm new myself so I am no expert, but I would recommend googling any questions you have to see if they've come up before. For example you could google (without the quotes) "gardenweb.com antique brass lighting in the kitchen" and you'll come up with some interesting threads. You could also search for "gardenweb.com mixing metals in the kitchen" or something like that. In your case, you are also looking for a specific type of lighting in a specific finish, so that's a question worth asking. Also, if you can't find anything recent on a topic, I'd ask it again. Times change and different people answer. If it's an oft-discussed topic people will let you know and perhaps provide you with a link to a past thread, but you'll also get some new discussion.

Here is a link that might be useful: Nauset Lantern Shop

I was just closing out my open tabs and found another company that offers pewter onion lanterns - with a major upcharge. Here's the link FYI.

Here is a link that might be useful: Newstamp Lighting

I never thought to Google a GW thread. Great Idea!! I normally search the website before posting but don't seem to have much luck. Those pewter ones are GORGEOUS, but so pricey! I was able to find a couple of black ones and I also found a VERY cool light that was made from an antique mason jar--that would be something different (link is attached below). I am still waiting for my sample to come back from the finisher, but the cabinets should look similar to driftwood, with a beadboard center. We have a slate floor and SS appliances. Kitchen paint color and backsplash is still up in the air, but we need a rough idea for the lighting so the electrician can come in and make holes in the ceiling before we finish scraping/painting it. Thanks for the input!

Here is a link that might be useful: Mason Jar Pendant

I like the look of brass (probably not the 80s shiny yellow gold looking stuff) with gray cabinets. We were specifically looking for burnished or brushed brass hardware for our potentially gray lower cabinet drawers. We found some but I think we're going another direction with a non-kitchen type pull that only comes in galvanised and we'll put that with whatever colour we end up painting the cabs.
I was going to suggest the Nauset shop that's already been linked.

I love the mason jar, but I wonder if the 40W bulb through the blue glass would give much light. Etsy is great, and that is a cool store. I'm sitting here wondering how I can fit the island falls clear chandelier trio into my house!

But I digress...With what you described you could definitely go with something in weathered brass.

Yes, those pewter lanterns are pricey. Why is it that the more expensive a light fixture is, the more I think, "I've got to get me that!"?

Good luck finding something you love!

I'm a fan!