Well, just remember that you could always be a huge douche and tell the NES to assemble sprites from 4 pixel units, and that can qualify as an acceptable workaround. You'll just be using a lot of green, black, and skintone the rest of the game. >_>
That pipe's a big improvement. If you tried your hand at some dithering, you could always go back to that matte look you had. My beef with it was simply that the shadows were awkward, and made it look flat. BTW, I'd recommend dropping the black border at the bottom of the pipe, as well. Since you'd be tiling up from the ground which already has a black border, it'll double the border and make it look off, when you want it flush.
EDIT: nvm the border, just saw you dropped it in your last pic, good job