If the tiles have any glazing, you can't "stain" or paint them .
And I doubt you would have floor tiles in a bathroom that are porous.
How about a nice indoor-outdoor carpet ?
otherwise smash them out and replace.
Tile refinishing is a job for professionals.
However, even those process, I don't believe are durable enough for
floor use to withstand the foot traffic.
Have a look here though
It's quite a bit more complicated than just slappin a stain onto it.
Search the newsgroup archives (groups.google.com) and see how many
folks have made the mistake of just trying to paint tile, and how
helpless the situation is once the paint starts peeling. :-)
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.