Don't really get why they are 6-sided dice, but they still look really cool. The only really big problem I see is that the wood grain is really wrong. It looks like the texture was printed on there. Try changing how the texture is on them, and you would have some incredibly realistic looking dice.
I like this image but the wood grain is simply wrong on the dice - it shouldn't wrap around like that. At a 90 degree meet point the grain should look like straight lines on one side and either dotted or spiraled on another side. Unless that is, the dice are somehow veneered with wood. Even so, the "wrap around" grain of the wood just doesn't look right to me. I would suggest grabbing a square piece of wood in real life and taking a close look at the wood's grain and in what directions the grain flows and ends. Of course this is all assuming you wanted a more realistic look to the dice.
Also, most dice only have a six on one side - not all sides. But of course you probably knew that.