I've seen a few guides on here on how to make wood grain but I didn't feel they looked like wood enough. This technique was learned about 5 years ago and I've never forgotten it. Hope you don't too. :)
This technique was made in Photoshop CS2. I tried to make it in The Gimp but I couldn't find the same filters needed. If you can do it in Gimp, I would love to know.
Step 1: Open a Blank Window
Lets start off by opening a blank window of any size u want. I used 800x600. Then, change the foreground and background color to a dark brown and light brown color.