Angela, I would use at least a satin finish. If it's a really steamy bath, maybe even a semi-gloss. It's hard to say for sure with so little to go on.
Indeed Is the ceiling in ok shape now or peeling and forming algae or mold spots. You may need to use a product with, or add, a biocide. Benjamin Moore used to make a special paint for kitchens and baths that had one incorporated. It had a finish somewhere between satin and semi-gloss and it was durable and easy to clean.
If the bath gets really steamy and holds moisture, you might want to add or enhance the airflow with an exhaust fan.