i used the Sound and Ambiance Improvement mod(ModDB) cant link though, since i didnt search for it.
But there is a HD Texture mod(think i found it through the forum though), improves textures to 1024k-Resolution. Which for a Quake4 based game is a little high for the renderer. But it adds alot of Sharpness and Smoothness to the textures.
Stone, Wood and Portraits look Excellent. Parallax applied as well.