There isnt really anything you can do then if you are on a server. Editing the png's will have no effect, as the texture would still be changing just to an identical image.
http://www.gimp.org/tutorials/@Thadius Faran :
But how do you actually edit the png? And I know I now sound like a noob, but the truth is, when it comes to texture editing I am even worse than a noob. So please help me (?)