Cool 3d effect! You left me a comment a few days ago about painting wood. This seemed like a good place to respond. You're off to a great start here. Now what you could do is use the brush tool with low opacity, and somewhat thin, with a darker brown color. Make curved streaks like wood grain. You can also make knotholes and other things. If in doubt, look at a piece of wood to see how the grain looks. After that, add a lighter color with the same brush, low opacity, still somewhat thin. Add the lighter color with loose strokes in between the darker strokes. Try to just add a small amount, don't cover everything that was underneath, just lighten it in the middle area between the dark strokes. With this lighter color, make sure you don't make a long stripe, just shorter strokes. Now (catches breath) Get an even darker color, almost black, and a thinner brush. Touch up the first dark streaks, but don't cover them completely. Just add little bits where they look too light. Also use the darker color to add details, like outlining the knotholes, and adding little flecks. Well, I hope that helps. Thanks for your comments. Keep painting!