mountains and sky have nice colors and work well together. trees are not so geometric usually. maybe you should take a look here on Pixeljoint I'm sure you'll find some great pixel trees :)

Usually people make cropped versions to serve as a preview image.

There is no point requirement to post on the forum as far as I know. Maybe there was just an error/bug that kept you from posting.

i tried to post in WIP, but i couldt because it seems like i need at least 6 points, also the preview image mus be 64x64 and i dont have the image at that size, besides thanks for the feedback

The rules require that preview images match the detail image, and yours don't seem obviously connected.

I think this is a good start! It's simple, but it's clear what everything is. The contrast on the grass, tree trunk, and dirt might be a bit high. Backgrounds should usually be more subdued, at least in areas likely to be overlapped by characters, so that the characters read clearly.

If you're looking for feedback, I recommend posting your works in progress on the forum. Since the gallery is for finished work, people are less inclined to give in-depth feedback here.