In this post I'm going to explain how to use crytif plugin on textures which are created using gimp. So you can use Gimp to create any kind of textures for CRYENGINE.
Create a shortcut of the rc.exe on the desktop. Basically it is located in CRYENGINE\Bin64\rc folder. Add this line next to the target path.
Then drag and drop your texture to the shortcut. It will open the crytif UI. Crytif automatically selects the suitable preset according to your texture names.
Check the 'List all presets' to display all the presets.