To me it looks pretty darn good. Perhaps the wrongness you are perceiving is the hard edges of the hills and grasses? I'd also suggest using a different background colour than white, or covering it up on the ground. If you are going for more realism then as it appears to be an area with regular rain fall I'd also fill in the open areas with vegetative colors and put some of the brown under the forests. There is also the issue of outlines which may be causing your issue, in that none of the ground features are textured or outlined like the buildings and trees, and there may be a style disconnect that doesn't feel right. Try outlining the roads and river and it may help.