Noisy Liquid in Motion Method
"What is the 'Noisy Liquid in Motion Method?'" You're probably asking. Well, yes, I figured you would. In this method, we go ahead and use the noise feature to lay down our high-lights and low-lights for us, and then create a complex Photoshop woodgrain by using the Liquify tool This method pretty much works for larger documents, and larger documents alone. The nice thing, though, is that you can save the woodgrain itself and apply the texture to smaller objects. Here we go.
Here I'm starting with a basic mahogany brown as my background layer. (HEX: #332119) Immediately after that, press D on your keyboard to set your active colors to black and white.
Create a new layer, and fill it with black.
Go to "Filter" and then "Noise" and then "Add Noise" and fill your layer with:
Monochromatic (Check this.)
Now go to "Filter" and then "Blur" and then "Motion Blur" and use these settings:
Use your rectangular marquee tool to select a part of the motion blur that isn't faded from the top to the bottom, like so:
Right click and select "Layer Via Copy" and then press CTRL+T to bring up free transform. Grab one of the side toggles, and pull your section across your canvas. You'll have something that looks like this:
(Afterward you can delete your old motion blur layer.)