The heightmap was made for 512x256 with a height of 40, though it should work at higher resolutions and be fine for all climates. I made sure to balance valleys with flats and mountains and islands.
Anyways, here is some screenshots from my play though before I corrupted my save messing with settings and adding/removing newgrfs.
I've also wiped up a scenario for it, Intended to be used with FIRS Temperate Basic, One nation has manufacturing, wile the other side has resources. One side is mostly coal, and one side is mostly iron. I suspect this could be a fun multiplayer scenario!
Incase I messed up the upload to bananas, here are the files.