Upgrade and add details into Level_2 sketch

I want to design the Level_2 background as the "underground world". So i upgrade the map into the underground and add the elements like the underground monster and the environment is the in the dust. Also, I set the light to dark because Level_2 is underground. Only can see through the lights. And then connect Level_2 and Level_3. I plan to set the background of Level_3 as the forest.