Not that this makes TOO much difference, and I haven't read all of the
replies here yet, but I noticed that my husband forgot to mention that
we live in the torturously dry climate of Nevada, and here they
declare 20% humidity to be DAMP(!)- go figure...we were actually
considering something like making a floor in a jigsaw-puzzle manner,
NOT a ripoff of ceramic tiles by making a bunch of squares.

I, personally, was thinking of marine plywood, or something comparably
resistant to re-shaping itself, cut to fit together and stained in
several tones, tons of protective coats, and then a thick coat of
something on top, like the 1/8" layer of clear stuff they pour on top
of bars and restaurant tables. It doesn't even have to be spectacular
looking wood grain - just so it's obviously some form of wood in
there. We're looking for a combo of inexpensive (at least RELATIVELY)
and completely unique, starting with a 10x10 foot toddler's room, then
maybe elsewhere if it works out well.

Thanks, Vegasdave's old lady ;D