Gorgeous fixtures. If you own the home and want to update, there are paint and compounds available that you can repaint the tile maybe a white on the wall and maybe a grey on the floor. The sink, bath and toilet can be re-enamel-sprayed to be white...

If you are renting and cannot change the color, I would suggest scrubbing the floor with vinegar to get them spotless and looking for something with the black, green and pink in it like...
Using something like this, gives you the binder for the colors in the bathroom. Towels and accessories, I would keep white. You could do a white shower curtain too, but bring in some texture if you can.

That sink is so fabulous! Not sure how much work you're wanting to do...keep the mint and go black and white everywhere else. Maybe take tile off walls and beadboard it? Take up floor and do in a black white penny or hexagonal tile? White subway tile could work too...do you have pics of the rest of your house? Would live to see the overall feel of it. Seriously, don't get rid of the mint-it can be really awesome!

Maybe these will provide some inspiration. If you don't love them, definitely know that they're desirable and you can sell them for a decent amount. I would love to have that sink in my upcoming remodeled bath!

check this out: http://www.apartmenttherapy.com/before-amp-after-a-period-bathroom-gets-a-charming-new-look-202252

One final thought-please do not spray paint or re-enamel them. That is turning something with great character and history into something tacky! I don't agree with salvaging all old fixtures but these are really special!

There is a whole section on this site for bathrooms: Retro Renovation

Agree with sargarsal, and also you could do a black and white or mint and white skirt around the sink to give you some hidden storage underneath, and then something matching for a shower curtain -- imagine this will take some DIY energy.

Hi
I like the retro bathrooms too. In looking at your picture, the white toilet seat should change to the same color as rest of toilet. You probably have to google it; hopefully, Amazon will come to the rescue :-)
On the right of the picture there is a partial view of something white. I'm assuming that's the door. So here are some pics for inspiration for the floor, door, paint, curtains etc.
Hope this helps,
Catherine

I just switched to a tiny sink, to make more space in the bathroom. I didn't want a skirt under the sink so I made a cute little cover instead.

It's just 3 wooden slat signs from the craft store, attached to each other with metal elbow brackets and then painted, and some embellishments glued on.

Whit and black subway tile

Thank you for all of the great tips! I do not own the house, just renting. Therefore, the only type of alterations I can make are adding decor, a new shower curtain, towels etc.

Just go with white then!

Vintage bathroom decor

I think you need to shop for a shower curtain in person. You already have green, pink, white and black for colors. Don't bring in any new colors. It might be easiest to get a mostly black or mostly white curtain.

Does the bathroom have shelves at least? I know a woman who has to keep things in woven baskets on the floor but at least she has a few shelves. Something like this will suit the room.

Do you know how to sew? If you do you can make a skirt for the sink and keep it on with magnets. Check first to see if a magnet sticks.

Some inspiration

I agree that it would help a lot of your toilet seat were green. I googled "mint green toilet seat" and indeed found a bunch, but from what I can tell color matching will be a challenge. Each one I saw online appeared slightly different in color, and if you don't find a pretty good match you still might find it annoying.

Take pictures of your fixtures and tile, including close-ups, and go to a fabric store and find a fabric that pulls the colors together for the skirt. When I look at your bathroom, I think "cottage" and imagine florals. But you might feel like doing something else that would look amazing. It would help a lot if you sew, or can find someone who can sew for you. If not, you might be able to do it with the iron-on tape that you can get at the fabric store, since all you need is a basic rectangle. Make it a lot wider that the sink measurement, and use a lot of magnets to create the bunched curtain effect.

Oh, also, I noticed your floor grout looks like it could use a good refresh. Something like Goo Gone Grout Cleaner might help your floor look a lot better. I found it at my grocery store.

Over the door shoe caddies are your friend, if you do canvas you can throw them into a front door washing machine. You can also use over the door shoe caddies between your plastic curtain and fabric curtain to store needed but not frequently accessed things.

It is a very interesting bathroom, I have never seen pink and black used with green before. Here are my humble ideas:

1. Scrub the grout on the floor and get it white again. My bathroom has the same sort of mosaic and it looked just as black as yours, but turned white (or at least off-white) after a nice scrubbing.
2. I agree with the green toilet seat, but if you can't find the right green, maybe a black would work? I don't see much white, but it looks like black is used for the soap holder so maybe it works better?
3. Get a nice fabric shower curtain and a plastic liner. I think white would work here. If you don't want white, maybe go with the grayish brownish color that matches your towels.

LAST YEAR'S DILEMMA, FOLKS!

Still fun to respond to the dilemma someone else may have a similar problem today and does not post. Don't rain on my soapbox.