KORD Grass Textures is it possibel to improve them?

I have just downloaded the super DXT Bmp reader that allows you to scan BMP images in the textutre files. I have done this because I want to improve / change the "awful" default groud textures around the KORD Runways. I have found the files in Cities/Chicago/Texture, but it looks as if they are scanned satellite images. I have even tried the simflyers KORD, but I notice that outside the main terminals and aprons they seem to use the same default satellite photo's. As I am a complete novice, can anybody tell me if it is possible to improve these images, so that the aprons around the runways dont have that funny speckled white / brown / green look?Best Wishes and grateful thanks,ChrisEGBB