Maybe you could get a little grow light fixture for a special plant spot in the bathroom. All you need is an LED lightbulb with full spectrum, or even just a "daylight" fluorescent bulb. You could leave the LED light on all day and it wouldn't cost much electricity. Could even put it on a timer. Then you could grow anything in there.
I grew cherry tomatoes and basil inside a little studio apartment with just a Home Depot shop light with daylight fluorescent bulbs in the middle of winter a couple years ago. Whole setup cost me something like $30 or $40. The trick is to search for "full spectrum" bulbs, or "daylight" bulbs and not use the term "grow light" because for some reason, if they call it a grow light, it will be more expensive. If you want to save some money.
Then, get some humidity loving plant and put your lightbulb over it. If you don't have much space, an African violet would be pretty and they're small. Maidenhair ferns are really pretty, but can get pretty big. If you wanted to get even more exotic, you could maybe even try an orchid.