If I wanted to carry out a project such as yours, I would perhaps try with a steam generating wallpaper stripper hopefully softening the adhesive enough to achieve the object but i wouldn't dedicate my life to the project!!
The only have I have ever attempted this was to be able to rescue a few tiles from one room of a discontinued pattern to use in another bathroom with the same tiles where I wanted about 40 more.
It is a thankless task, unless they are poorly stuck on.
My success rate was about 30%, and the task involved chipping off the tiles with a bolster then grinding the adhesive off the back.
Unless you have a similar scenario to mine, it really isn't worth it, as others have already said.
buildersmate, a long time ago I was told a trick to help get the adhesive off old tiles. Soak them overnight in a bucket of (originally) warm water with a couple of spoons of baking soda added. Next morning the old dried adhesive is gooey and comes off a treat with a scraper.