What makes a good bathroom plant?
Two things: it should love humidity, and it should tolerate the light your bathroom actually gets. The plants here all prefer high humidity, which a bathroom supplies for free. Match the specific plant to your light — a windowless bathroom needs a low-light-tolerant pick plus, ideally, a grow light.
Do bathroom plants still need watering?
Yes. Humid air keeps leaves happy and reduces brown tips, but it does not water the roots. Check the soil as you would anywhere else and water when the top inch is dry — humidity just means you can usually water a little less often.