Imagery
Sometimes you can't find exactly what you need. GET HELP.
Photography  Textures
Textures can really enhance your design project, if used appropriately. They can create depth and realism to your design. You can layer several textures for a unique effect or just use one for a straightforward design.
Finding Textures
Here are a few free websites that provide textures, but if you can't find the perfect one you can always create your own using a scanner or camera.

Texture King (All Hail)
FreeFoto.com
(also has textures)
Smashing Magazine (Don't be discouraged by all the ads, there actually good textures on here).
Mayang's Free Texture Library

Rule

Using Textures
Be wary of being too heavy-handed with textures, you want to enhance the design and intent, not distract your audience.
Texture
Creating Textures
If you can't find the perfect texture for your project, you should try creating it yourself. The best way to start is using your digital camera, here are some helpful tips:

 Make sure the lighting is even before you photograph (no glare or shadows). Try photographing on an overcast day.

 Check if your camera has a close-up or macro setting, this will help get details up close.

 If you need a texture of a something flat, like fabric patterns and graph paper, try scanning it at a high resolution (300 to 1200dpi).