To add new textures to Syntensity and to your maps, do the following:

• Prepare the textures themselves, in file formats appropriate for the engine (see the sauer editref document).
• Create a Package.js file, that does the texture commands.
• If you have a sauer .cfg, you can convert it using tools/convert_cfg.py
• If not, you can use tools/create_tex_cfg.py to create a new one, but it assumes a specific file naming convention (see that file for more; also, see the existing texture packages - /gk/ in particular - as they use that naming convention and had their Package.js created using that tool)
  
• Make an asset containing the textures and the Package.js, and set its location to something like textures/USERNAME/texturepackname.tar.gz
• To use the textures in your map, make the textures a dependency of the map asset, and run the Package.js command with Library.include('textures/USERNAME/texturepackname/'); (note the trailing slash, to indicate it is a directory) in your map script.