How fun for you.......
I have friends who are doing the same thing in Bass Lake California. I love staying at their place to see the latest improvements.

I recommend that you do hardwood flooring, drywall on the walls ( painted a light beautiful color ) and tongue and groove wood on the ceiling. The light colored walls will keep the space bright and cheerful and the wood on the floor and the ceiling will give you the woodsy feeling.........

Were you going with wood on the wall, I would still have a couple of walls with sheetrock just to lighten the room up.

For flooring, a 3.25" solid wood flooring would look great. There are the more rustic versions that would really add a lot of charm to your cabin. My only advice is that you need to make sure you buy a high quality floor, not from a big box outlet like Lumber Liquidators or even Home Depot as their wood floors aren't dried properly so you end up with a lot of problems. And don't be fooled by 55 and 100 year warranties--they're basically worthless, and designed to protect the company, not you.

We just ordered our solid hardwood flooring, and went with Mohawk 3/4" 3.25" solid white oak. We haven't started our living room floor yet as we're finish up our kitchen. Here's a link to it, and Mohawk's site--they're having a sale the rest of the month.

http://www.mohawkflooring.com/hardwood-search/Belle%20Meade%203.25%22/White%20Oak%20Natural/?return=hardwood.aspx||qwe=|solid=1|pp=25

Be sure to not go with a floor that has an aluminum oxide finish on it as it's so hard, it can't be refinished because it destroys sanding pads.

I guess I should've specified that we can't do drywall because we are post on pad construction, which shifts too much in our climate (we are in the Canadian Shield)

I'm also looking for ideas of what to do around the wood-stove where that grey board is

Would bricks shift around too much near the stove? If sheetrock would, that probably would to.

Have you googled building on post on pad construction to see what others have done? I'm sure there are lots of people who have cabins in the wilderness that have blogs or youtube channels documenting what they're doing. That's where I'd start.

I love the board and batten look for your cabin.

You could also go with board siding. It can be installed horizontally or vertically. Stain or paint boards.

Colourwash:
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Studio1001, that's great! Tongue and groove pine or cedar seems to be the way most people go, I'm not crazy about the way it looks normally. I've thought about painting the wood but didn't want to risk hating it

Cork floor would work well too, because it can float. Anything like brick or tile that needs mortar would likely shift, although a small area like that might not be too bad. Do you have any pictures of what you were thinking about with brick, I'm picturing 80's fireplace in my head!