MysteryMeat: Turf roofing is really good, cheap insulation. In Iceland, the idea was taken a step further, with
turf being used for walls as well. On the back side, they are built up against a hill for even more insulation, so it's just the narrow front of the house that gets a relatively-uninsulated wooden front.
OP, remember: that's
turf, not just
grass. Without the dirt to give the grass a place to root, there's nothing to provide that insulation
and the grass will die. Give that roof some thickness!
Also, consider not leaving the walls blank wood, unless this is meant to be a poor person's house (in which case it looks pretty fancy, with its two finely-made chimneys) - walls were whitewashed, painted, etc as much to protect the wood from rot and water as they were for decoration. Places where untreated wood was common were usually either devoid of any materials that could provide such protection, or poor (or the houses weren't expected to last more than a few years anyway, as e.g. in the case of nomads or places with many earthquakes).
The cast shadows on the roof and walls don't seem to follow the forms of the material, they're just straight-edged triangles. Cast shadows only have straight edges if they're falling on completely flat surfaces! The grass would break up the edge of the shadow, and the shadow would seep into the cracks between the wooden beams a bit (and if they're meant to be a bit sounded, the shadow would have a wavy edge).
In addition, your cast shadows being triangles doesn't make sense in the first place. Think about where the light is coming from, and where it's hitting. Remember, shadows are the result of objects being 3D! Don't just think in terms of flat shapes, think about the 3D forms making up your scene, and how they interact with light. Shadows aren't arbitrary, they're determined by the form of the thing casting them, and the direction(s) of the light.