There is a couple of ways to do this. The first method involves either going out and taking pictures of interesting textures- such as fence palings, grass, gravel, pebbles etc, or downloading textured image that a photographer has released for public download (please read their conditions of use). You can find such images here: The Ephemeral Victorian, The Lune Rouge and Wetfish scraps. Please note if there is conditions for commercial or personal use and ABIDE BY THEM.

• If the photo you have taken or downloaded is coloured, open it in Serif Photoplus ( or your image editor), select the Image menu, then Adjust, then Grayscale.  
• Now open a new or existing image 12″ x 12″, 300 resolution. If a its new image, fill with the colour of your choice.
• Now open your texture image file, copy.
• Now go back to 12″ image, select paste new layer. If smaller than 12″, stretch to fit, or tile it.  Your textured image should overlay your ‘paper’ now
•  Go to your layer manager tab- making sure the texture layer is on top and selected.  Now muck around with the options in the layer properties drop down box, and the opacity value.
• Find something you like save it or export it under another file name and keep playing.. you can get a plethora of papers!!

Let me know if this is helpful… And please always read the conditions of use when downloading images from the net! DON’T BE  A PIRATE!