inside sto's folder is one called localdata, basically a place to put mods. as long as the proper file structure is in place it will load what's there overriding the packed files.
ex: H:\Cryptic Studios\localdata\texture_library\costumes\Avatars would contain sub-folders to alter various race/gender specific textures relating to what's worn....only you see the changes however. thought that was one of the best things they did....one of the strangest was textures are in .wtex~>.dds with a wrapper that probably adds functionality for their engine. but makes it less straightforward to mod.