Ok, so the 12 year old has committed in her heart to transforming her room into a steampunk oasis. We picked up some antiques for her, a good Art Deco vanity and dresser as well as a bed.
Now we need the accessories. And she believes you guys are the help we need. Wallpaper, light switches, fixtures and so forth. Can you guys provide some guidance?
Cafe Press has a pretty decent selection of steampunk dodads - especially things like wall-clings and posters (so if/when she gets past the steampunk phase, it’s easier to move on). They’re pretty cheap also - at least the artwork and decorative stuff seems to be.
I would also check out ebay - search steampunk furniture or steampunk decor and see what comes up. Perhaps try those phrases on Etsy also, but watch out for price and people selling stuff they picked up at craft stores and re-packaged and are selling for way more than they should be.
A lot of the specific stores that sell “steampunk” either have very shoddy stuff, or its very overpriced (at least IMO) and I wouldn’t want you to drop a bundle on something like that.
If you have a local flea market or there are estate sales where you are, I would seriously consider having her go with you to one of those and see what old crap you can pick up on your own, and then she feels like its more authentic and vintage. I have a horrid old moldy suitcase (like, an actual suitcase, with coathangers and drawers and all) in my garage, and it’s the coolest thing ever, because I’m the one who found it at the sale, and I won the bidding on it.
I’m currently in post-production of a steampunk short film, so I’ve made some amount of investigation into this.
Steampunk means many things to many people, but I’d cling to Jules Verne Science Fiction as the guide - 1880s aesthetic with a futuristic twist. Brass and polished wood, decorative and hopefully practical. I don’t have any specifics regarding furnishings etc, but here’s a funny music video that may be a guide.
How about this switch and this plate?
etsy.com would be where I’d start.
Some ideas:
An old map
Chandelier light fixture (Olde worlde light bulbs are available too)
Mirror
Clock (the more exposed the workings the better).
You probably can’t do much with the existing windows, but maybe with some stickers you can do something like this.
Definitely look up how to steampunk things yourself. There are many sites for DIY Steampunk, and that way she can contribute and feel like it’s something made rather than something bought, as that’s something that fits into the steampunk ethos. 
I’m no help, I just want to say I think it’s cool you’re helping your daughter have the room she wants. We just finished transforming my 14 yo son’s room into a “rocker kid” bedroom complete with dad’s old bass as wall decor. Lots of fun.
This blog is written by the woman behind Cake Wrecks. She’s very interested in steampunk and in crafting, and has a lot of different posts either describing various steampunky projects or showing the work of others. She has a whole steampunk dining room and a number of other objects throughout her house.
IMHO the best steampunk decor is 80% Victorian with carefully selected steampunk accents. It’s easy to overdo it otherwise.
Tell her to take whatever and Just Glue Some Gears On it (And Call It Steampunk).
I heartily second this post.
I heartily third this event or product. Steampunk is not about wearing a top hat with gears glued to it!
Really, what I would suggest is primarily using Victorian or Victorian-inspired stuff with a hint of SF here and there to spice it up. Gluing nonfunctional gears to everything looks really lame.
Does she dress Steampunk? Hitting the local thrift shop and buying her some long dresses and having her tuck an iPod in a brassy metal case into the belt could go a long way.
Remember that Steampunk is about SF too - see if you can steampunk some functional items like the aforementioned iPod or a desktop computer (casemod frenzy!)
I think she’s too young to join, but Second Life has a number of steampunk themed areas such as Caledon and New Babbage that you could check out. New Babbage focuses on the inner city/industrial side and Caledon is more focused on country estates. Unfortunately, a fair number of people walk around these areas wearing top hats with gears stuck on them, but there’s plenty of inspiration to be had.
This is a great time to get her some basic electicity and mechanics learning kits - have her understand the basics and then she can create her own stuff. If you trust her and can work with her, perhaps even some basic plumbing and soldering so she can add metal and tubing to whatever her creations might be. There’s lots of interesting - though not always useful - stuff on Instructablesthat can help her learn too. Take this opportunity to make your kid smarter, as well as cooler! 
Meh, gears aren’t steampunk. Just attach a bunch of pressure gauges to everything and you should be done.
If you wanna go to New York and have some serious scratch, there’s this place. Some of it’s well done, some a bit much. I am not sure about the toilet lid on that second bathroom, though.
New Babbage? Was there an old city of Babbage? I call my house New Schwarzenegger… or can I?
Neither of my boys have caught the Steampunk bug, but my daughter has it. I’m making her some goggles for Loot Day.
Keep in mind that Steampunk was originally more than just an esthetic, it was also part and parcel of the builder community. It’s nice to be able to buy these things, but even better is learning how to MAKE them yourself. A good starting point: There are a ton of YouTube video’s teaching how to dress up and paint various Nerf guns into Steampunk inspired blasters or what have you.
For the sake of creating the right atmosphere in the house, this ice coffee maker fits right in. Some engraved brass plates might add to it, but it’s pretty nice on its own.
no steam but fits anyway
But if you have lots and lots of extra money, this one is way cooler
