The only thing that is really ugly with this bathroom is the floor tiles and old shower screen. I'm all for getting new shower screen install. Repaint the whole bathroom with tile paint and for the floor get good quality water marine grade merbau timber and put timber decking over the bathroom floor. New shower head and tap fittings if you see fit.

Sounds like a very stressful situation! If there is absolutely no way the builder will allow you to change things (even if they did, I imagine they would ask you to foot the entire bill of pulling the tiles down and replacing all water proofing in addition to new tiles), I can make a few suggestions for improvement. Firstly I would suggest replacing the tiles above the vanity with a white mosaic, a patterned or a textured feature tile/strip. You could also use this same tile to replace the vertical feature in the shower. There are some beautiful shapes and sizes available to choose from. Secondly I would address the grout situation in this way: Floor - dark colour grout & Walls - Light colour grout. Lastly if it does not prove too difficult or expensive, maybe replace the tiles below the vanity with a plain white tile (could be similar size). Good luck and I am sure once you have a lovely mirror up and some crisp white towels, it will look just wonderful.

Hello! Lovely space, I have a huge soft spot for these bathrooms. To honour what it is, but make it more enjoyable for your uses PLANTS PLANTS PLANTS. I would either install some shelving to have some dangling vines (or equivalent look) plants up high, or use a hanging fixture into the ceiling. That far corner above the bath would be great. + A large (and tall) pot plant and some smaller ones wherever you can fit them. On top of this, I would replace the doily curtain to a more modern look, perhaps white, wooden blinds? If you can do further work from here, it would be accessories, like the towel rail, and tap ware. Something a little Art Deco for your taps would look amazing. Finish with large, fluffy white towels and bathmats to conceal as much of the colour as possible and brighten the space and a big candle or three, maybe a white stool or ladder too.

All the inspiration photos are definitely walk in showers, with only a shower screen, no door. But you are correct, all of those photos the bathroom appears to be wider than your plans. For example a bath is usually 750mm to 800mm wide. If you use that as your approximate measurement then each of the inspiration photos look to be more than 2000mm. This is allowing for entrance to shower space, 700mm to 800mm and then 1000mm to 1200mm for shower screen.