I have been playing a little bit with texture in photoshop. Here is a very easy one that I did today. I get my textures from www.mayang.com/textures/. This is a picture of Smoky and Takota I took this winter. The picture was a little washed out so I messed with curves in lab color mode to bring out some color and contrast (Make sure you switch back to RGB mode when you are done). I then took a texture of some gouged dirt and made it the same size as my photo. Then I used the move tool (upper right hand corner of the tools) to move the texture into the photo. If you don't like the colors of the texture you can change it to grayscale to delete the color information. I then set the layer to overlay in the layers box and set the opacity to about 67%. Smokey's face didn't show up very well so I used the burn tool at about 19% to bring it out a bit. Not too compicated, but I like how it kind of makes the photo look old.
Takota is my aunt's new horse. He is a six year old mustang that can be very stubborn. He is also not very fond of having his picture taken. Smokey, on the other hand, was always posing for a shot. He would stop, look at me, and wait for me to take the picture before going back to chewing his grass.