These are extra textures for the texturizer plugin.  When you choose "load texture" you can load a file in *.psd format.  These psd files will extend the functionality of the texturizer.  The advantage of using these textures is that you can choose a color that goes with your image with the eydropper tool and then apply a texture to it.  This saves you time because you don't have to adjust the color of another background texture to match your picture.  These are samples of the textures in the zip file.  You of course, can choose any color and then apply the texture.

 These are all seamless.  However, you will have to look at the file name to see the height of each fill.  If you see 100, or 150, 200, or 300, that is the height of the file.  Most of them have the same width.  Make your strip a height that is divisible by that number to get a seamless texture.  In other words, take the number in the file and multiply by 1, 2, 3, or 4 etc.  Use format/dimensions to make your strip the right height.
 

How to make your own textures.

One thing I have found about making your own textures, is it is important to have a good deal of contrast.  I used the format/focus command to sharpen them, and also increased the contrast through the color bar.  If there is not enough contrast, the textures won't show up well in the texturizer. If you think you have one that will be a good texture, save it as a psd, then open a new canvas, the default size.  Fill it with the color of your choice, and apply your new texture to it.  You can do this with the psd file still open.  If you find you need more contrast,  go back and increase it, and save again.