When you replace the fixtures, tile the floor..use larger tiles..small tiles will make the space seem smaller.

I would tile the floor with a dark grey and paint the walls a lighter grey. Fluffy white towels would be perfect then.

I would paint a more inviting color than gray. I know it's trendy right now, but I think a light shade of turquoise would be warmer. New flooring would be good.

There were three more images that initially were supposed to be there, too. Just to show what we've got to start with. Small and unappealing.

New flooring- scrape and repaint flaking walls.

Make it as elegant as possible since it is the only one and small.
Be sure it smells really nice too!

I just notice there is no tp holder. The stuff on the back of the toilet makes it look cluttered. Even if it is a tp holder on a stand, you need one.

I notice your sink is a modern style that doesn't go with that great claw foot tub. I would replace it with a more vintage look with chrome and a storage shelf underneath it. New flooring and some subway tiles on the wall and this could be great.

^^^
Oops forgot inspiration pix.
http://houzz.com/photos/575075

Liz, do you have a picture with the light turquoise you are describing? I've never heard turquoise described as warm.

Paint the bathtub in white or even a color ...keep the floor choice simple..add nice baseboards

Do a beautiful paint job on the walls and add a fabulous antique mirror over sink

Fresh new paint and shiny new fixtures is all you need to sell. More money spent will not be recouped IMHO.

I agree with Darzy!