The windmill is just very small, that's why it doesn't look right. Try making it to the sale scale as the house. Windmills are typically quite large because they need large sails to work.

The house and trees are in different scales. The door is about the same size as the smaller trees, which means the trees are person-sized. If you go for a more symbolic look that can be fine, but judging by the level of detail and the fact that you have larger trees, you're going for something a bit more realistic. In that case, your single-tile trees should be young trees and bushes, not miniature mature trees.

The brick wall looks flat because the bottom and top of it are flat and don't suggest the curvature that the lighting seems to. See how you've made the small trees have curved bottoms/layers to show that they're seen from above? You can do the same thing with the wall and anything else that's curved.

The large tree in the right mockup is lit from below, unlike everything else.

I think the windmill with the white sails looks good, though it should probably have a roof (or some remnants of a roof if it's meant to be ruined).

Are you aiming to make these scenes to-scale or not? I don't know whether to give you feedback on that. It looks like you're going for some vague sense of scale with the buildings, but not the environment, a la SNES RPGs?
Don't get me wrong, that's perfectly fine. I just want to know what your goals with that are so that I can avoid giving you useless feedback.

The walkway looks nice, though you may want more variant tiles. It's easy for patterns with combinations of large and small elements to look repetitive, so it's best to have a few different tiles to mix and match.

I prefer the old house door. The middle one reads more like a ship hatch., and the large dark areas on the left door look like they're open gaps into the dark inside, so it doesn't look like a solid door. The two other doors I can't judge, since they're presented without context. They could be good, though the right one with the simple outlined cross-bar looks a bit boring. The others have more volume and character to them.


I didn't give you feedback on everything because there were many things where I wasn't sure which item you meant, or what you were going for with them.