You don't say if you have any natural light at all in your bathroom. Obviously a real plant will need some natural light to survive. I have two stems of curly bamboo in my bathroom, they're doing great.
If you do go artificial I would also say don't have dried flowers,and if possible go for fake plants that have smooth plastic leaves (not flowers), as they're much more cleanable. I have several matching this description from Ikea (in bedroom, kitchen and living room - can't vouch for how they do in bathrooms with all that "magnetic" dust).