What kind of old hanging ceiling light can I use in a bathroom?

I would try looking for old ones at Good Will or consignment shops~ a lot of times you can find them online from people remodeling as well. Home depot calls them pendant lights and they have a lot of them online to look at. Hope this helps some

You can use a pendant light anywhere however, if you use your bathroom for applying cosmetics and other light sensitive purposes as trimming hair, you will need more light than a standard pendant light can provide.

Dependent on taste you can get even a Ceramic 1 Bulb with Outlet fixture and Screw in a 3 Bulb to 1 Adaptor to place that lamp on a dimmer switch as: ranging from 30 watts to 300 watts by Using any Dimmable 100w Equivalent LED Bulbs.

Few know these adaptors exist but they do. Let me refer you to Some Goodies at Amazon Lighting Department that you gotta really dig to find:

Bulb Adaptors:

https://www.amazon.com/gp/aw/s/ref=nb_sb_ss_i_0_12?k=bulb+adaptor+socket

Faceplate adaptors:

https://www.amazon.com/gp/aw/s/ref=is_s?k=wall+outlet+shelf

Porcelain Lamps:

https://www.amazon.com/gp/aw/s/ref=is_s?k=porcelain+lamp+fixture+bulb

I am sure you will more pleased with those than a Pendant Light:

https://www.amazon.com/gp/aw/s/ref=is_s?k=lamp+pendant

If the wiring is already there you can use anything you but if you do not have wiring you'll need electrician to run wiring. Needs to be safe. when you are hanging new fixture make sure electric is off. SOME ideas https://www.youtube.com/watch?v=S_D2zg4kmTc TIPS https://www.youtube.com/watch?v=9PUCo2aXVAU more https://www.apartmenttherapy.com/8-diy-ways-to-upgrade-ceiling-lights-246541 https://www.homedit.com/21-creative-diy-lighting-ideas/