The first thing that comes to mind with the tiles are concrete stepping stones for the garden if you have enough. Or you could make some 'mosaic' wall plaques or frames and cut the sheets into different sizes/shapes.
A table top would be nice too with some sort of creative base...A lot of possibilities! You don't have to just think flat either, you could make a cylinder shape for a table or bird bath base with the tile on the outside. What a lucky find. Be sure to post what you end up with!
JO

Also, if they have a slick finish, you might have trouble getting anything to stick to that surface & stay. If your project is a decorative wall piece, it wouldn't get much wear, but for something like stepping stones, the surface would likely wear off.

Try a small experiment & see what works before you put a lot of time & effort in.

'Pup