well it seems there is a lot to comment on, i think i can start at a high level and as things progress more detail specific crits would probably arise,
my main response when first looking at the image is that it all looks to me that things lie on the same plane of existence, the grass looks like it is at roof's height, and the only objects with any real depth are the trees. If you incorporated some of the same shadows behind other vertical objects/structures, such as the houses and bushes, it would help to distinguish depth for them as well.
the grass, as you are going with bladed grass, i think utilizes some strong contrast. if you push the shadow tone a little lighter, i think that the grass effect will then look subtle enough not to steal away the visual attention it currently attracts.
The water looks a bit like a mirror, i think the dark underlines which separate it from the dirt around it give it an embossed effect, which is clearly not what you are trying to do... to be consistent with your tree light sources, the shadow would be cast on the surface of the water in its upper and left boundaries (not the lower and right boundaries)... and make sure you dont do it in a way that makes it seem outlined as is currently shown. also, this outline effect near the edges of the roads look a bit too strong to me as well?
perhaps you could provide a mockup with some ofthe characters on there as well
the picket fences i feel are just too dark against the rather vibrant green, and have an effect of being pushed 'into the ground' if that makes sense, i think when the pickets are that small they shouldnt be outlined, else you get that separation from the fence away from the rest of the environment, which at this scale would not work very well.
