You've got a good eye for contrast, especially with the pallete you chose. A lot of the stuff that tries to emulate 2D sidescrolling games I notice don't tend to take that into account. It can be so absorbing to get all of the little details right, that a lot of people forget to take into account how it will look once there are characters and objects running around on it.
Although I don't know if that's what you were going for here. Even on its' own, independent of any character sprites or objects, it looks good. It's important to know when to stop trying to add more detail before a picture gets cluttered.
The rope mount thing is out of perspective with everything else.
The pillars, ground, and rope all appear to be out of perspective, and the really rocky tile looks like a more suitable ground tile imo.