There's perspective conflict on the buildings. On the top-center piece, you have diagonals that are conflicting with the bottom walls they're overlapping.
Probably be best just to remove the diagonals all together, cutting it off at the vertical.
. . .
Great job on the detail, but at this level requires a great deal of work.
However if you feel comfortable with it, then stick with it (just warning).
Shadow from the tiles onto the wall is needed, and from the wall onto the grass.
The grass tiles are also very busy compared to everything else, and reveal tile outlines (diamond diagonal) if you look closely.
. . .
I'll try to do a bit of work on the sprite for you, and get back if I can.
Novice here too, so take my advice with a grain of salt.