I don’t think a designer can ever have enough images in their repertoire. Enjoy these links.
Texture Palace:  Premium free textures.   Grunge, concrete, metal, ink, stone, textile, and others.
Bgrepeat:  Free repeating backgrounds.
Squidfingers:  Free repeating backgrounds.
Dinpattern:  A great variety of repeating backgrounds.  Be sure and read their usage policy.

Backgrounds, textures, patterns, and seamless tiled images can really make a website come alive and compliment your site content.  Many sites offer royalty free images and have a tremendous variety to choose from but I also like to scout out images on freebie sites as well. Below you’ll find links to just a few of these sites:

Texture Vault – You want royalty free paper, paint, dirt, mud, glass, concrete textures? They have it, plus some.
BG Patterns – Create your own tiled background – fun and free!
The University of Texas at Austin – Historical maps, maps of the world, countries, cities, states and more in the Perry-Castañeda Library Map Collection. Most of them are for use in the public domain.
Texture King – Grunge, dirt, plaster and more – free!
Bit Box – Lots of textures,  the site owner  calls himself a “Freebie Maker” and he likes to give away only the best quality stuff to help designers – free!
Outlaw Design Blog – Vectors, wallpapers, grunge, icons, fonts, and more – free!
Pattern Wall – Seamless patterns – free!
Wallpaper.net – Wallpapers and stock images – free!
Veer – A large selection of royalty free images, illustrations, typefaces and motion images.
Punchstock – Over 2 million royalty-free photos and illustrations from Jupiterimages, Getty Images, Corbis and over 50 other brands, all in one convenient search.
Urban Dirty – Textures and stock photography – free!
Morgue File – Large public image archive for your creative work – free!
Dreamstime – Royalty free and free stock photography
Tartan Maker – Generate seamless tartan patterns – free!
iStockphoto – One of the largest royalty free stock photo, audio, photography and motion image repositories on the web.
The Inspiration Gallery Many lovely textures including some outstanding damask images – free!
Stripe Generator – Generate seamless striped background images – free!
Stock.XCHNG – Large selection of stock photos – free!
Fotosearch – Search 5.3 Million Stock Photos, Stock Footage Video Clips, Royalty Free Images, and Illustrations
GraphicRiver – Royalty free graphics and illustrations. Launched in February 2009, the site focuses on premium design components like Layered Photoshop Graphics, Vector Illustrations, Icons, and Adobe Add-ons like Brushes, Patterns and Textures.

There is so much information on the internet to the point of oversaturation but once in a while I will come across something that is just jaw-dropping creative. Here’s Aviary’s description in their FAQ of what their apps do:

What is Aviary?

Aviary is a website for artists of all genres to create, edit and share their works directly in their favorite browser.

For instance, take a look at the creativity that went into changing Hillary’s picture.

They are taking Early Bird Invitations for beta testing their products too.