IIRC you can extract all the textures from your SH3/GWX installation using SH3 Extractor.
Just point it to your installation when it askes and then extract all the textures to a separate folder.
Once they are all extracted, the folders/structure will named the same as the original.
So you will see a folder called druck7_CR.dat and in there will be all the textures you need.
To work with them or create new, you need a image suite which works with TGA files.
Once you have finished, create a folder structure, like this (Name of Mod\data\Textures\TNormal\tex folder) and place your new TGA files in there. Then enable with JSGME.
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