Jits said this on the other thread, Ill leave it here until he gives an official update of some sort.
''As a general rule of thumb:
Take a screenshot.
gl_highres_textures 0
vid_restart
Take another screenshot and compare the two.
If the textures look pretty close, you should be fine. If not, you should probably change them. If you really like the textures and feel they're better than the official textures, post about that texture (or textures) in the official HR4 pack thread. In the mean time, I guess you can post a screenshot of the low res and textures you want side by side here, but I'd much rather focus on improving the official pack rather than approving alternatives.
Really, everybody should use the official HR4 pack as a base and only use custom hr4 textures for the textures that have not been completed yet. Provide feedback on the textures you don't like. When the official pack is completed and enforced, you really have no right to complain if you provided no feedback.''