HI FRANKY
This is what i did for those 2 scenerys to work change the geo file exactly and I mean exactly as below.
you dont have to change anything else m8.

LIGHT_POSITION 0 0.20 -0.40 1.00 0 <--- this goes in place of existing LIGHTAMBIENT
LIGHT_AMBIENT 0 0.99 0.99 0.99
LIGHT_DEFFUSE 0 1.00 1.00 1.00
LIGHT_SPECULAR0 1.00 1.00 1.00
LIGHTAMBIENT 0.7 0.7 0.7
LIGHT1AMBIENT 0.2 0.2 0.2
LIGHT1DIFFUSE 0.5 0.5 0.5
LIGHT1SPECULAR 0.9 0.9 0.9
LIGHT1DIRECTIONTHETA 45
LIGHT1DIRECTIONPHI 360
LIGHT_AMBIENT 0 0.99 0.99 0.99
LIGHT_DIFFUSE 0 1.00 1.00 1.00
LIGHT_SPECULAR 0 1.00 1.00 1.00
LIGHT2DIRECTIONTHETA 45
LIGHT2DIRECTIONPHI 0

And what you should have in the scenery directory is your named scenery folder ie delfgauwluchl&gras
you must take out of this folder and leave in the scenery directory 64 x 64 bmp the 256 x 256 bmp and the geo files. this worked for me see screen shot

hope this works for you m8

Regards Dave