You want balance for your particular project and not to just follow some generic rule of thumb.

Do a scaled diagram to see what size looks best and where it should be placed.

This is what I did, a diagram laying everything out with exact dimensions. I tacked a copy in the bathroom, so there was no confusion on where I wanted the trades to place things.

I am having a problem with my Publisher program trying to convert to jpeg, so I took a photo of my screen.

End result. Not everyone will like the same things or same proportions, so do what looks best to you, and works best for your space and your needs.