[Above] Mat Vintage European Oak floors from Berti Studio.
I have been in love with grey/silver floors for a long time and even considered installing decking (real wood) inside, and hope it silvers over time - as it gets washed with water and soap - as a cheaper (maybe?) way to recreate a barn-ish look. It would also be a way to bring the outside look: in. No matter what you decide, I think mat floors are very 'Austere chic' - especially if you like the "Barn/Farm/Shaker/Industrial/Cottage/Hampton/English Garden/Provence Garden/Japanese/Lofty" look (sorry, but I can't quite make up my mind on what I like best).
Another floor that almost always looks good and is full of soul is waxed concrete floors, but they are harder on the back, especially if you walk barefoot as much as I do. However, if you happen to be lucky enough to have old concrete in your crib, like friend and architect Claude suggests, you can seal off the concrete with linseed oil (add at least a third of turpentine so that the floor doesn't remain sticky), and that will give it a beautiful sheen (applicable to wood - especially wood - as well) that will repel most stains. Linseed oil smell divine, too, and of course ... it is eco-friendly!
I will add a few more posts on painted floors, sub-floors as actual flooring, decking, etc ... stay tuned!