You could add a Venetian mirror about the size of the window to balance the look on the wall behind the tub. Glam and symmetry. See below example. Best of luck!

http://houzz.com/photos/15283502

Place a large painting equal in size to the window on the empty wall

Thanks I was thinking to add a mirrow. Should it be the same style as the vanity mirrow ? Thanks

This incredible ! How did u do that?

Beverly can u show me what would u do? What about adding more marble on the wall?

I agree. Not another mirror please. Too much going on already with these mirrors and the window being there.

For an inexpensive fix I would put some green behind the tub, either a fake or real tree that is low light. Greenery softens an area and that would help bring focus to the space as a whole. I'd go with a tree that reaches as tall as your mirror's height. This image used an orchid but it's a similar idea

For a little pricer change, I'd add another window.

What about adding something simple like this? A simple wall decor. It doesn't have to be this one. Just an idea for you.

If you have PAINT from Windows adding the additional items is copy, trim and paste.

There are videos on YouTube to explain PAINT.

Not sure how you would start and stop marble in that location.

Another option could be maybe a wall hung short baker's rack that could store towels and bath accessories.

Decorative gear mounted on wall, or shelves to hold towels and toiletries

After looking at the pictures I agree you should try some greenery there to balance the window. It might take a few tries to get the right container, height and greenery type. It could be that tan/beige tall grassy works. IMO the tub should be the focal point, not the corner behind it.

P.

If you do decide to go with a mirror, I would go witH the second example photoshopped by Beverly. It doesn't have to be Too literal and be the same shape but imporTant that it is to scale with the window. Best of luck!