I have used Steam to clean some things that were dirty to a point you'd not believe.. It does not often discolor fabric, I'd be careful using it on a ceiling though cause if you melt adheasives bad things happen. but it shoud work properly applied.
Be very careful you do not steam your fingers, it will cut the flesh off the bone.
One time at a towing company where I worked for a while I took my steamer (A Euro Shark "Canister" type) in and cleaned the toiled.
When I entered and plugged in it was black
about a pint of water later it was white.
Water, that's all I used, water, 220 degree water.