Patterns are a useful resource for website design in today’s market because filling a background with a full-blown image is not a viable option. A variety of devices and screen resolutions make up today’s market and your image may not be able to adapt to them all.
Instead designers and developers can use a variety of patterns to form backgrounds for websites. Patterns are similar to those images that can be replicated indefinitely horizontally or vertically, and thus represent one major theme across the webpage.
This makes a lot of sense when one is trying to convey a solitary but background thematic. A number of sites collect and make available patterns for free use to aid in your designing of websites and pages.
So while Colour Lovers focuses on color contrasts and patterns, Subtle Patterns works on suggestive ideational patterns. Sites like DeviantArt and DIN Pattern work to create complex patterns that can be used to create themed pages and websites.
You could even go for something light and breezy and funny from a number of these sites, such as Brusheezy, which have a distinct cartoon character in many of their patterns.
Regardless of the type of design you need, most of them are available for free online downloads, with Creative Commons usage. You could contact the websites, give them your feedback and also ask for specific designs and patterns, though these may not come for free. Get working on using patterns to design your website!