1) rotate the wood on the side of the planks
2) make the ladders consistant, some of them have skinny boards on the side and the others are thick, skinny looks nicer
![Smiley :)](Smileys/dp2/smiley.gif)
EDIT:
3) Pure black on the sides of the wooden elevators looks really bad, use wood or metal.. or anything else
![Smiley :)](Smileys/dp2/smiley.gif)
4) in the tunnels add some real light sources, just using the light entity with nothing looking like it's emitting light look bad. There's no laziness in mapping
![Wink ;)](Smileys/dp2/wink.gif)