Heya. I don't know which site you might have seen these on but I'd guess they were created with Genetica. I'm pretty sure they're not from photos.
Here's the link to the software maker's page (Spiral Graphics): http://www.spiralgraphics.biz/genetica/gen3announce.htm. The top end gets a little pricy (I'd love to have the studio version) but the basic version is only $149 (okay, still pricy, but worth every penny if you need textures). There's a demo on the site.
Edit: Oh. I didn't realize it but it looks like they have a ton of free textures available for download on the site: http://www.spiralgraphics.biz/packs/index.htm