I've checked some forum threads on this topic and I found some say it's not a W7 compat issue, but a problem with modern GPUs. According to PCGamingWiki on Quake 4, "Modern high-end GPUs with a lot of memory can cause Quake 4 to ignore any other quality preset than low quality".
Fortunately they give a mini tweak guide on how to add some commands via an autoexec.cfg file you make. This allows the game to load textures properly. The guide is also more comprehensive than any I've seen mentioned in forums.
I've checked some forum threads on this topic and I found some say it's not a W7 compat issue, but a problem with modern GPUs. According to PCGamingWiki on Quake 4, "Modern high-end GPUs with a lot of memory can cause Quake 4 to ignore any other quality preset than low quality".
Fortunately they give a mini tweak guide on how to add some commands via an autoexec.cfg file you make. This allows the game to load textures properly. The guide is also more comprehensive than any I've seen mentioned in forums.