This is a small tutorial how to easily do wood in Photoshop. I made this in 5 min and it could look better if I put some time on it
Anyway, here we go:
1) Choose a good wood color
2) If you want it to look like planks then do some dark lines in it. However, this can wait till your done with the wood texture
3) Go to filter/Noise/Add Noise and make it look like this
4) Go to Filter/Blur/Motion Blur. set the angle of the blur to the angle the trees' fibers should go. In this cause it should go straight up but if you do like a pillar or something to tibia then it needs to go diagonal.
5) Make some shadings around the dark lines and then use dodge next to the shading to make it look like the planks are sticking up.
6) Add details. Making a mark of an old stick really makes it look more alive. Also... if you weren’t completely satisfied with the fibers you can use the pencil tool with black color and 5% opacity. Make some lines on the wood and don’t make it look perfectly straight.
This also works in small formats like 32*32