Are you still working on this? I see that you are also a member of Modders Group on Steam, if you wish, I can help you with the ground textures. I was also working on a similar "season" but was having trouble getting the Atlas to match the LOD Atlas_Billboards, ... hard to tell what tree is what tree in the billboards. Ground textures are not a problem, same with Skyboxes. A Spring Mod would be great too.
Additional thoughts
In response to #1: If that is the older "Sunrise" Skybox for Train Fever (DasMatze?), it is a lower resolution than the ones used in Transport Fever. (TpF uses HDR files for the Skybox and HDR files generally contain a bit more data than a .tga file.) Shameless Plug: Try my Sunset mod on the Steam Workshop.
Ich arbeite an einer Reihe von Frühlings- und Sommerbäumen mit Blumen. Es ist jetzt bei Steam erhältlich.
