Alright, two weeks have passed and I feel like I just have to make a progress update. Now, with the usual disclaimer that everything here is work in progress and is subject to change, lets begin.
First of all I want you to notice the pixelization effect I made, I think the game will be made with this kind of artstyle in mind.
Here are some pines that I made:

And some ordinary trees:
And some more trees, they are a bit different and I hope its noticeable:

Some rocks, surprisingly tricky to make:

And some bushes:

Some tree stumps, with and without mushrooms growing on them:

Some sticks and logs with a dead tree:

And this is all that I have made so far. Of course, this doesnt mean that I'm done with forest assets, on the contrary, I have plenty more ideas, so I think I might give another progress report in a week or two.
With all that said, cheers!