Lucian86 & Fed1
thanks for your feedback. Unfortunately, it's impossible for me to do better than the current ground textures by myself ; I slightly improved the grass one by adding dirt patches, but this was the max I could do.
If you know someone that can do better, I'll be happy to see the result ; I could even pay a few bucks. There's one important thing for the clay texture : it requires a decent normal map, else it'd look very flat without one, or weird with a bad one.
However for me, the current ones are quite decent, plus they are consistent with the rest of the visuals, so it's alright.
And yes, I plan to to give the possibility to Mod them, for the people wishing to do so.