[Jhoffa_]

But how do you carry replacements for 25,000 different tiles?

Obviously, you cut them to suit.

What do you do when you break a ceiling or floor tile? Order one casted, flamed & delivered to fit the hole?

[altair]

That many different tiles takes up space and weight and costs delta-V. The space shuttle is already too expensive in terms of cost/weight to lift things into orbit, carrying all those backup tiles would make the problem worse.