No definitive answers here...I'm still seaching for the right stuff my self. My sister and her husband just installed cork flooring (in their case, 1' x 2' rectangles) over the concrete slab in their basement. It followed the uneveness of the floor just fine, it's really nice looking (can be stained or painted) and it's warm (even in stocking feet). I guess in Europe they've used cork flooring for over a hundred years and a lot of museums do too. Here's a link for the flooring
I'm also looking into Marinedeck 2000 with uses cork strips (maybe 2.5" wide) alternating with poly strips (ony 1/8" wide); ends up looking like a Teak & Holly deck in a nice boat. Really durable as the cork is rubberized and the poly stips take a beating.
For the ceiling in the bus I'm going to use roll cork (from the same place that sells the cork rectangles ) as it's thin, has a good R-value for it's thickness, it's a good sound insulation product, and it's light. Again, it can be stained or painted; I haven't decided which since the natural color of the cork is pretty light but maybe an even lighter coat of paint will be in order.