Everything seems to have the same priority, by an equal amount of contrast. This puts everything on the same level, and makes the picture lose any sense of depth. It's really hard to look at.

Like Manupix said, think in terms of volume, some thinks are clearly going to be in complete shadow (you probably wouldn't use more than 1 or 2 colors for these areas) , and others are going to receive a lot of light, if you're going to use an entire range of light on an object, it should be something that wants the viewers attention.

Doesn't work so well, it's quite noisy.

Try to have some simpler patches where the eye can rest, esp behind the sign (almost can't see it!). Less / better grass, smoother / larger rocks, more fluid water. Think volume, and keep some places in shadow to make it apparent.