Rather than painting over or removing tiles from a bathroom is there anyway I could plaster over tiles or would the plaster just fall off.

Honestly I can't think of a way to plaster over tile unless you prep it first and how to do that depends on what or where you are going to plaster, am I right to assume it's a wall or walls you want to do? What part of the house or building is the wall in? Bathrooms are different than kitchens, patios, living rooms, etc. Think about what the plaster needs to adhere to, chicken wire, perhaps putting up a net of chicken wire over the tile first will give the plaster enough footage-but that's only an idea don't hold me to it. Personally, I'd rip out the tile and depending on what's underneath and where its located, put up new board and chicken wire. Good Luck.