For class..
Here is a link to free textures:
http://www.flickr.com/photos/chorando/sets/72157607835630011/
1. From the main single-view page like this, right click on the image and choose Original.
2. Drag to your desktop or right-click Save As….
3. Open one of your shots in Camera Raw, make edits, then open in Photoshop.
4. File -> Place the texture you downloaded.
5. Adjust the size of the texture as needed. Hit “Enter” to apply changes.
6. In the layers menu, change the blend mode to Overlay. (You can also try Screen or Multiple or others to see how the effect changes)
7. Save As… JPEG.