I've seen it 'planked' w/a strip of the same wood. You'll want to experiment w/the stain and finish coloring before you just go out and do it. Buy an extra piece for testing IF you decide to go this route.
I've see it tiled too. Depending on the room involved and what rooms 'surround' the problem area, your taste for tile should 'fit in'.
Other than that, I've seen it carpeted. You can carpet it (in the meantime) until you have a more permanent idea.