Use porcelain.  

Subway tile is cheap but why not do large format porcelain tile in white to reduce grout lines, for example.

I like ceramic or porcelain time, though.

Porcelain tile is probably best from durability standpoint.But let's consider that you're covering over an existing floor.

And I wouldnt go smaller tile, Id go bigger and porcelain not ceramic and be sure setter butters backs of tile.

The part that goes in the toilet has a rubber coating on it so that you don't chip the porcelain when you are working it.

I have dark walnut porcelain tile floors, expresso cabinets, pendant lights, light granite counters, white walls.

When you are this far, and you orient the toilet straight and tighten down the bolts, but not too loose so the toilet won't rock and not too tight so you don't break the porcelain & with the tank far away enough from the wall so you can fit the lid onto the tank but not too far away so it doesn't rock when people sit on the thing and when you connect the tank to the bowl you remember to use the rubber ring and when you insert the ballcock stem you get a good seal and you set the water to stop before it overflows the tank when you turn the water on and you use plumbers tape on the threads when you connect the hoses, you should be fine.

Apologies.If its a cleaning issue that is not harmful, and no, what looks like mold in the bathroom needs a porcelain cleaner, not bleach, and a wire brush....

IMO, I'd go with an indoor slip resistant Porcelain Floor Tile.