Yes i think one of the reasons the top one is so much scarier is because the walls are so dark, as if something could jump out at you from them at any moment. Everything also seems colder, and because there's less life in the background, you'll be really freaked out by the actual enemies popping up through it. I think the pig looks far better in the first one aswel, because the player will be staring at it wondering if it's part of the background or not. Reminds me alot of those freaky sepia pictures and whatnot.
Btw it's great, not so keen on the sprite though.