Nice! Im kicking this off then!
I'll just start by taking some pale ochre, mix it with a little ibt of grey, and just paint in som happy little tree trunks
So if you're all cool with it, my idea is a tileset with the main feature of modular trees. Each step up shrinks the width of the trunks by 2 pixels wich allows for building nice natural looking trees. I suggest that we add some personality to the branches and tuning the color. And we also need to add some ground and grass and plants and all that schtüff.