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!

You could do a wet room on the south end of the room with the tub and shower combined to conserve space. Window would go above tub, however with privacy in mind it would not be low as you have in your cad drawing. see photo. Vanities would go on the west wall with toilet on the east wall. I am guessing at the dimensions because you mention meters and in the US we use feet, but it sounds like about 9'x15" ? The location of the entry door really impacts the layout of the room, but it looks like it cannot be moved.

Third vote for getting a professional involved, but i'll still offer my layman's suggestion given that you're just soliciting general ideas at this point. If it was my space, I'd switch the bathroom and the laundry room around, keeping just one of the walls currently enclosing the toilet. Its hard to estimate precise measurements from the drawing, so it may not be feasible, but here's what i mean

Your client putting trust in you was the right decision! amazing transformations! Love the natural light in particular as thats a great spot for a post gym pump flex for a good selfie!