What are you creating textures for exactly? Seen people use varying programs with GIMP having great capabilities. Would recommend photoshop, but that is a very expensive program to use if you're just doing this as a hobby. Cost me $700 for CS2 then just recently was lucky enough to upgrade, but it cost me $175 so that's $875 investment.
Would definitely give GIMP a try since it can do a good chunk of work that photoshop can, but lacks more advanced tools from what i've heard.