I would replace the tub with a clawfoot tub for the farmhouse charm. White subway Tile in the shower surround and go darker on the floor. Try to find a tall cabinet furniture piece to house all the bathroom supplies. Paint your vanity and get new hardware, matching faucet. Replace lighting and for warmth consider a fan with a heater built in. Stick with alot of white than you can choose your wall color, maybe a yellow.

http://www.google.ca/imgres?imgurl=http://cdn.sheknows.com/filter/l/gallery/country_decor_bathroom5.jpg&imgrefurl=http://www.sheknows.com/home-and-gardening/home-d-cor-styles-gallery/country-cool-d-cor/country-farmhouse-bathroom&h=460&w=360&sz=46&tbnid=c7gi74v_yhYRvM:&tbnh=100&tbnw=78&zoom=1&usg=__XQwD_dddGtJ7pUnmpyO04K8Wu58=&docid=NtpbJffKAQqaPM&sa=X&ei=mX5oUdzKFeW70QHj6oHICA&ved=0CDUQ9QEwAQ&dur=1746
You could try this site for ideas

I would remove the light fixtures as the ones in the photo look kind of clunky and heavy.
The towel bar looks kind of lonely there by the showerstall. You can install one of those nice long towel bars on the other wall.
A smaller mirror & cabinet.
Maybe, even changing the cabinet color to a darker modern shade to "warm up" the room a bit.