HOW TO MAKE A TEXTURE PACK

Maybe my tutorial could help a little bit.
It's in German language, but maybe Google can help a little bit.

Eigenes Texturepack erstellen

its realy not that hard

fist you need to install a plugin that lets you edit DDS images in Photoshop or install a image tool that can edit DDS image files
then you can use 7z to open the textures.jar file, Note i said open not unzip

Once open find the texture you want to edit and double click the image, it should open inside photoshop, where you can edit it and then just click save

for DDS plugins for Photoshop try this link https://developer.nvidia.com/n…ure-tools-adobe-photoshop

The files are showing with a DDSE extension. I have a DDS editor but I get the error: Can't read file header.

Do these have some special encoded or something? If so, what editor can I use to and add new DDS files?

I want to try adding some more clothing to the list.

Which files exactly are you talking about? I know Photoshop can for instance open and save DDS files with a plugin.

Adding more clothing items (or any other kind of items) is not possible at the time, the only thing you could do is changing the textures of existing clothing items. To do that extract the texture you want to edit from the jar file, edit it and then repack it in the jar file replacing the old one.