FreeImages.co.uk

Free images is a high quality resource of digital stock photographic images for use by all.
All images are free to use on websites and printed materials.
http://www.freeimages.co.uk/index.htm

  Netscape Background Sampler

As the title suggests a "sampler" of backgrounds.
http://home.netscape.com/assist/net_sites/bg/backgrounds.html

  Media Links Free Backgrounds & Textures

WOW ... Huge collection of free backgrounds and textures by several great artists.
http://www.erinet.com/cunning1/textures.htm

  ER Backgrounds & Textures

Over 375 backgrounds and textures indexed in 12 easy to use different groups. A Texture View has been added to the Background section to allow you to evaluate what the texture would look like on a page.
http://www.ender-design.com/rg/backidx.html

  Art for the web

Offers a nice selection of backgrounds and other graphics such as complete page templates.  A bit slow to load but worth the wait.
http://www.webpagedesign.com.au/