First, I added random colored lights, so each room would have its own feeling to it:
|Random colored lights|
The next thing I added was a basic character controller (the model is still a placeholder), so that I could walk around and see how everything looks.
I put in some walls and rendered it from an orthographic camera in 3D:
This little video shows everything I mentioned so far:
I also started adding more parameters and randomness to the level generator to make the levels more interesting. Writing code to create random dungeons is not very hard, but doing so that you get predictable and consistent yet interesting results isn't that easy.