A scale drawing is always helpful, however, a bigger question for me is whether you are planning to rip out fixtures like the tub and toilet. I am going to assume that you prefer not to, but would offer other suggestions if you are planning to rip those out. The first two things I'd change would be the vanity and the flooring. Swap out the flooring for something more modern like large porcelain tile. Get a modern sleek vanity, preferably with two sinks. Make it large enough to go the whole width without the little blank space to the left where you currently have the trash can. A small trash can can always be hidden in a vanity door. I'd stick with white for the new sinks to tie in with the other fixtures. If you find a white vanity you like, fine, if not, think of it as furniture rather than a part of the bathroom and allow it to make a statement.

Change out the light fixture and frame the mirror.

If you have the funds to do it, I'd also get rid of the glass doors on the tub and install a new tiled surround that coordinates with whatever flooring you select. They make all kinds of wonderful tiles, including gorgeous glass tiles, but do keep in mind that whatever you choose you have to clean (or have cleaned, if you have someone who does that). Because of that constant cleaning and water spot issue, I'd avoid shiny glass tile, no matter how tempting it might be. Then use either a fairly plain fabric shower curtain on a curved rod to add a feeling of spaciousness. Keep visible products to a minimum, preferably in attractive dispensers you refill set in built in nooks in the proposed new tub surround.

It would a bit of an indulgence, but that space under the window would be perfect for a wall mounted towel warmer....

Definitely get rid of the too short curtain on the window next to the tub and replace it with something that will block people from viewing you without blocking the light.

You don't show a picture of the alcove where the additional window is, but it looks like it's probably a dormer. Since those tend to come in multiples, make sure that whatever window covering you have on that matches the other dormer(s) for curb appeal. If there's sufficient space in that alcove a small makeup table and stool would be great there with the natural light.

Have fun with your project. Don't forget to post after photos so I can admire it!