One thing about your tiles:
The log you can stand on is darker than those in the background, which is quite fine IF you make all foreground objects as dark, however, the background appears to have a higher contrast. Things with high contrast will appear as foreground component. You need to think about how this works in real. Close objects are dark, have high contrast - far away objects have lower contrast, are probably a bit lighter and fade towards 128,128,128 grey so they are dull as well.
Use inbetween steps, maybe even having a foreground layer of objects that are more or less shilouettes in front of the actual playing field. Shortly said: make clear distinction betweenl layers of tiles.