Finding that great background pattern for web application is hard and sometime very daunting task. We all have been there. We spend hours to search around for a decent background pattern, but we usually end up with patterns that are either too much on the face or have quality leaves much to be desired. I just found a great online resource which has huge collection of professional quality patterns for designers and developers. You must checkout SubtlePatterns.com.
One feature I like most on SubtlePatterns is that I can click on the preview button of any pattern and I can see how that pattern will actually look like as background of the page. What a great time saving feature! It happens a lot to me if I am very particular about the pattern I want use on my web site. I found a great looking background pattern somewhere, but when I drop that pattern on my web site, it comes out to be too dominating for the page. With preview functionality, you can see how that background pattern will actually look like before downloading and implementing on your web site.
You can use patterns from SubtlePatterns in commercial projects as well as long as you provide proper credit SubtlePatterns.com somewhere in the project.