I've been using found textures for YEARS and I recently found some really nice ones on Brooke Shaden's site. So, in the same spirit of sharing and playing nicely together, here's some high-res greyscale textures that are free to download and use for anything you like (personal, commercial - whatever) all I ask for is a link back to this page so others can find and use them.
Here's what they look like:
SW TEXTUREPACK 01