What made the difference between Wolfenstein and Doom, beside the fake 3d, was the "movable stuff". Even in Doom 3, machinery make for a big part (transforming you and so on)
Now I understand that DoomRL is top down, but still. Movable (or rather, sliding) walls could easily be done. The walls would crush you of course if you are in their path.
Movable floor (up/down) could be doable too. Someone would need to find a way to make a "middle" state in ascii. They would be the normal "." when up, maybe a darker one when in the middle, and it would be replaced by lava characters when completely down (thus hurting the player). What would be cool is if the blood and the objects would dissapear when the platform comes back up (lava is hot)
What would be cool is some sort of rotating "gear" like walls. Going round and round.