One of the most difficult kinds of textures to find is Denim (Jeans). I had this one project in which I just had to use a good, quality denim texture, and I had to look for it really bad. Thankfully, after a little hard work, I managed to find some really great texture, which I share now with you!
These were all found at Flickr, so you should check their status for commercial use. Just click the image and check it out at a bigger size. Also, check out each author's page. Anyways, I hope you find these handy and useful. Cheers! ;)