Can I install 6"x8" ceramic tiles on painted ceiling?

What is the ceiling material, drywall?

How big an area? Normally you can't do this because the weight will pull the drywall down. If this is a small shower area, put in backer board, screw it well to the joists and then install the tile. Even doing this you can't be sure and it will be hard to hold the tiles in place until the adhesive dries.