I have found this great site with free quality wallpapers: www.wallpaperstock.com .

It has great wallpapers and it is updated daily with new ones. The site is clean and easy to use. Visitors can also submit their own wallpapers. The only bad thing is that the site doesnt have a search function.

looks like a nice site to find walls, but take care, any further ad about the site will be considered as spamming and will be removed without notice