Good morning! First of all, don't paint the entire banister black! This would be too dark paired with the dark wood floor. From looking at your photos, it appears that the rest of your trim is white, so I would leave the staircase as-is (the white spindles compliment your other white trim, and the dark railing and stairs will compliment the dark floor). On the carpet ... of the three choices shown, I would choose the lightest of the three (which looks to be the center sample) -- this would bring out the lighter brown/gray color in the dark wood floor, and would show up better on the dark stairs (the dark carpet with the dark floor will be too much dark). Another choice would be a patterned runner -- this could be a subtle pattern of neutrals, in a traditional, transitional or contemporary design, depending on what else will be going in your room. Also, I would leave the edges of the stairs exposed, as they are now. Hope this helps!