This replaces the built-in PK01 texture set with the original TGA textures downloaded from philipk.net. Texture resolution is doubled on each axis and there are no more JPEG compression artifacts. Sauerbraten-specific textures (individual trims and glowing red panels) were recreated accordingly.
This was tested on all maps. It works OK on most maps, but a few maps have texture alignment issues on replaced textures due to voffsets not being adjusted for the new texture scale. Unfortunately, this can't be fixed without distributing modified maps, which would trigger "modified map" errors when joining multiplayer servers.
PS: If you can find high-quality texture sources for other texture packs that are included in Sauerbraten, let me know in the comments :)
Installation
Extract the ZIP archive and place the packages
directory in your Sauerbraten user data directory, which is located in:
%USERPROFILE%\Documents\My Games\Sauerbraten\
$HOME/.sauerbraten/
Merge the directory with existing files if there are any.