I think the problem is that the colours come out as noise rather than the grain of the wood.
try keeping it simple, separate the shapes with some dark black or dark, less saturated brown and try to make every pixel there for a reason.
depends on the style you're going for, but here are some good wood/crate examples using very few/simple colours. the last one is good detailed planks.
www.pixeljoint.com/pixelart/29352.htm
www.pixeljoint.com/pixelart/40038.htm
www.pixeljoint.com/pixelart/29480.htm
tsutsu-di.deviantart.com/art/Pigrate-ship-85438881
(props to the artists above)
oh ya, don't forget some nails! :)
Its pretty much looking like copy and paste and then rotation.
I prefer the preview, because at least between the clicking of it and the completion of the loading of this page it maintained some semblance of hope that the full image wouldn't invoke design principle violoation regurgitation.
Needs to look less flat too...which could be doen with some contrast,as said below.
really god texture :)