Your use of perspective is great in my opinion, and the sprites/people/animals are fine
But one point of criticism to share would be the trees and landmarks
Simple shading will not do without strong contrast to outline leaves in the trees or ridged rocks in the mountains
I'll lookover it, see what I can do during free time then post when there's sufficient updates
For now work on those points of critique and adding definition to your rivers and land then we'll compare our updates
Fair warning: artists here tend to avoid minimalist topics such as these
Possibly from it being both time consuming and frustratingly limited, even more so with color restrictions
But then again so is most pixelart, so who knows
However there are certain projects to pull advice/ideas from
These use similar miniature tilesets as found in the submission
Older Final Fantasy games also had miniatures on their world maps