All 3D artists should take as many photos as possible which they can later use as textures, but for those of you who haven't done so, here is a link to a new and very useful online texture library.
It is called Texture Pilot and it has some great source images for textures, and what's more, registering for the service is free. They give you a 20MB download amount free per day. And if that's not enough, you can elect to have loads more in return for an annual fee.
So, no excuses and no moaning about not being able to find any textures!