
You could perhaps try to separate your foreground and background elements more in the cave areas. As it is, the ceiling blends in with the back wall of the cave, and those stalactite spikes on the ceiling are barely visible. (I had to zoom in to actually see the little ones) I would argue this would be very bad if the spikes damage your character if he touches them.
I assume that you're trying to separate the back wall of the cave by making it darker than the foreground, which is not a bad idea. But the problem is that all the colors you have right now are all 100% saturated brown shades.
[edit:]

By simply de-saturating the background layer to almost grey, I've already brought some definition to the ceiling of the cave and the other foreground elements. However, the darkness still makes the tones of the stalactites blend in with their surrounding area. So it might be better to lighten the entire background up some.
[edit:]

Now the stalactites are easily visible and hopefully easily avoided.

Of course, you may want to keep the background of the cave a dark brown color for aesthetic reasons, but you can still hopefully use my tips to add definition to the playing field.