argh, some wrong RCs @carlit: to change the ground texture you just need to go to the map folder and take the ground you want and give it the same name as your existing ground texture. @carlit again: no problem, its not to tell you its bad, its just to help you understand how easy it is to change these things :)
I think the mainly used ground texture on this map is something like ../Program Files (x86)/Catching Features/maps/dyynimaasto6/detail_leaves_and_crass.jpeg. You can replale it with whatever other jpeg with the same name (and about the same size and resolution).