There is a big trend in using ornate background patterns in the last few years. Vintage patters are also making a comeback as well online as well as in home decorating if you happen to watch How Not to Decorate or Home Heist.
So as you can imagine you can use patterns and texture in a variety of ways in your designs, as well as offline in business cards and other marketing collateral.
So here are two sites to help you find a style to go with.
Pattern Head is a lot like iStockPhoto, but for patterns. The patters are seamless, meaning they repeat on all sides to create a seamless pattern. All patterns are supplied in both vector and raster formats and all patterns are royalty free.
Squidfingers has a lot of free patterns that are in a more pixel art style that might be more suitable for various types of sites.
You can also find patterns on various stock sites that sell illustrations and photos. iStockphoto has a good selection for example.
For simple stripes the much luaded stripe generator is a good tool as well.
It never hurts to play with pattern and texture, just don’t overdo it.