With a nice clean space like that you can go a lot of different ways. I would start by looking at shower curtains, because they can become the focal point. When you find one or two (or more) that you like, you can play off of the colors in the curtain to find the color towels, bath mat, and even wall color. Some ideas: You could go classic black and white, with a touch of something bright if you want for an accent (like the fuscia in the photo) Or something "spa-like," in acqua and cream. Or you could go bright, with teal and lime green. Another classic look: tan walls, white and/or tan towels and bathmat, simple white accessories. Good luck!

First and foremost - what are your plumbing facilities and where are they located. This may have a large effect on what you are able to do.... I have transformed a bedroom to a bathroom and some creative returns and plumbing were required. Also are you intending to add a toilet?

Do you want this to be a big reno? meaning, will you replace things totally or do you want to work with what you have mostly? will you add a toilet to the bathroom? if you replace the vanity, you can put in a larger one curving around the corner with a medicine cabinet above. If you replace the shower with one flat on the ground, you can also put in clear doors for bigger visual space. how about re-painting as well

Great home. I have an outdoor shower was I live adjacent to the beach but only ever use it to wash our feet. It is hard to keep the metals used maintained. I like the idea of being under the stars but in reality i think i would rather have a different vibe than an indoor bath. A spa or jacuzzi adjacent to a pool is potentially more social. Overall a nice extra but certainly not instead of an indoor bathroom especially in the winter time.