Low poly Alabama

this is my second big project in blender and I want to make it as good as I am able.
I lived 4 years in Birmingham Al and recently moved to the UK. My friend who left in Birmingham sent me a post card with her drawing of our fun time in Alabama and I decided to visualize it in Blender.
1st picture is her drawing and 2nd one is what I have so far.
I think I missed something and it doesn’t look stylish.
I know I need to change some shapes and materials but have no idea what exactly. Maybe trees need more work on them…
Also I wanted to add that I used ready models of a human and a horse but eventually I am planning to redo them. And probably I am going to make clothes for people (4 of them are representing 4 of us) and I don’t know if I need to do it for low poly style.
Any help and critique, please?

Everything that’s there so far looks good as far as the low poly look goes.

My humble two cents:
It’s hard to be sure, but I think it might help if you fleshed out the outside of the Alabama region. Not so much that other parts take focus, or even have any actual content in them, but so that the state is more comfortably placed into its space.

I can’t tell if you have a small amount of shadows or if it’s all just rough reflections on the ground, but you might want to play with adding more visible shadows.

And if you’re going to keep the captions, you could also start playing around with adding them and see if that helps you figure anything else out.