Well, unfortunately, there isn't much I can do to make it look better without drastically changing it, or making it worse than it already is. Also each texture did not start out itself as square, some were a little longer on the sides than they should be. I'm guessing it came directly out of Half-Life itself.
I still did try though, I up-sized by approximately double (each square is 512x512 pixels now), and then I used Photoshop on each square to attempt to unblur the images a little bit, but I did not get much success with that. I will try again more when I get some time. In the meantime I'll send you the work I've done already, though it may look worse than the originals.