I was asked how I made my Valentine texture sign, <3 U.
I shot a concrete wall that has great textures. Played with it. (See last blog post). And it looked like this.
I opened it up in photoshop and added a new layer that looked like this. Just black and white.
On this layer in went to the layer selection tool and picked difference. (Photoshop CS, see below)
You can see that the sliders are all kept at 100 percent.
It looked like my final image.
I hope this helps you to start thinking in the wonderful world of textures.