Without seeing pictures of the rooms in your house you're trying to flow with, there is not much strangers on the internet can tell you based on the pic you provided.

I can tell you that your 6-panel door and medium oak flooring is pretty traditional, transitional at best, so I don't see the problem as maybe you do since you're there and can see the rest of your stuff. That wall paper is beautiful, and the hexogonal pattern in it makes it transitional. Honestly, I don't think you'll have a problem. Get a sleek white toilet, maybe go for industrial/modern hardware in an antique bronze finish, white vessel sink, dark wood stained countertop or maybe an interesting dresser turned vanity. Just mix it up.

I would use it on the same wall as the toilet. One wall only. Maybe use some modern hammered gold accessories to bring out the gold in the wall paper. Simple gold fixtures.
Perhaps some green leafy plant to add another color. White towels in a basket to keep it fresh:)

I love the idea of mixing this pattern in with your decor. There is always room for something traditional in my book. I did something similar in my hallway powder room and only had one bad review. It was a vertical stripe in a Ralph Lauren-esque pattern, but I was tired of the art nouveau in my house. Maybe it's too overwhelming in such a small room? If that's the case, then maybe add a board and batten on the lower half of the wall. I say go for it! It's a small room and can be easily changed :)

I'm not sure why you feel the need to coordinate with the rest of the house..it's a bathroom. Maybe it's just me..anywho..Your wall paper is really pretty. I agree with another post who said go for it and although gold is not a favorite of mine, I can see it looking beautiful with this wall paper. Note on BRONZE FIXTURES. I have them and they are harder to clean than the silver/nickel ones. The ones in the sink are good (so since you said you have no shower, you're good to go if you choose them) but the ones in the shower get soap muck on them almost as soon as I clean them. Would like to see a post of the after once done. It will feel very Victorian and beautiful I think. Good luck.

Strangers on the internet! haha!!! @jess13

you could use the plum color and/or the hexagon shape as a repeating motif in other adjacent areas, but in a more modern style. I like some traditional things with modern, it makes it look less museum-like.

At first I was onboard with comments about gold fixtures to match, but I looked back at your wallpaper and it appears to be more cream than gold, so any metal will work. Go with more modern fixtures, and grow the modernity with the artwork you choose. I immediately thought of http://postercabaret.com/ when I read this. Good luck to you!

I agree with Jess13's suggestions. Some sleek modern fixtures with dark wood traditional-ish vanity would be cool. I would personally like to see a gold faucet, but I know it's a fine line between "fancy" and "1980s" when it comes to those.

Just go shopping - if you were drawn to that wallpaper, you'll probably be drawn to whatever goes best with it. Don't worry about whether it "goes" just get what you like.

It won't clash. Do the whole bathroom with the wallpaper. It will be its own little design ecosystem and work wonderfully.

Here are some thoughts:
- Put the wallpaper on the ceiling
- Put the wallpaper on the inside of a bookshelf or a glass front cabinet/hutch; Here is an example, http://www.apartmenttherapy.com/east-2-malindas-black-white-bo-40952
- Put it on whatever wall you want but accessorize that area/wall with a few very modern pieces/accessories like a bold lamp; I love this one, but wish it came in other colors, like aqua or yellow, http://www.zgallerie.com/p-8266-mariposa-table-lamp.aspx; I guess you could paint it.
- Search for wallpaper on Pinterest or Houzz for ideas from all the photos; Look for non-traditional uses, something unexpected.

Good luck! I'd love to see how it turns out!

FYI .... those ideas are for rooms other than the bathroom.

This is a great opportunity to go neo-traditional. Your house clearly isn't "modern" in that it isn't minimalist. Neo traditional takes the classics and reapplies them for today's aesthetic.

For example you could do the whole bathroom in this paper, but instead of matching with gold or violet towels, choose chartreuse towels and some abstract art with plums, greens, yellows, and oranges for high contrast. Install super minimalist towel rods and sink hardware, and select a modern light fixture.

Neo trad design is about contrast and contrast. Here are some fantastic examples of neo traditional design.

http://tinyurl.com/avoajol
http://tinyurl.com/ahbmct6
http://tinyurl.com/ah5g4nw
http://tinyurl.com/amqk4ts
http://tinyurl.com/awvgcjj
http://tinyurl.com/ardfgga
http://tinyurl.com/a8wy8tj

PS sorry, I meant compliment and contrast.

ugh, complement... can't spell today

I don't think it has to go with the rest of the house at all. A powder room can be a tiny jewel box in its own right. The small size allows you to experiment with rich color in a way that might seem over the top to you in a larger room. Your paper is really pretty. It will also transition fine from the gray paint in your hallway, when you have the door open.

For some reason, when I went house hunting 5 years ago, all the houses which I saw with powder rooms had the powder room decorated in a way that stood out from the rest of the decor. I always imagined that was what you did with powder rooms.

That said, this poster is decorating a small bathroom, which is a bit different. Still, I see no reason why you can't have different flavors of decor.

If you want to update the wallpaper, another option you have is framing it. In this case, I think a really long frame (like one that would hold a full-length mirror) would work well. However, that might look a bit more modern rather than contemporary.

Also, if you frame the wallpaper, you can take it with you. Another cool thing to do with it is make multiple frames with it and add hooks on it (e.g., for bathrobes).

If you move, you can take the frames with you and then use them elsewhere (like in a mud room)!

You might find some ideas here: http://www.casasugar.com/Coveted-Crib-Mark-Homewoods-Mod-Victorian-1500745?slide=2

why wouldn't a picture of the bathroom be posted? seems silly.

I think having something like this in a sleek modern bath would look great and interesting.