Simple but good: checkered Photoshop design patterns. I found this one on Brusheezy and was created by RubelCreative. It’s a simple set of three patterns in different styles: (1) plain, (2) shiny and (3) slanted. I wouldn’t use these as-is, because a harsh pattern like these can become pretty eye-diverting. The way I implemented the shiny pattern was to set its blend mode to Overlay with a solid color underneath. Turn down the opacity or fill a notch for good measure.
Download this pattern here (Brusheezy link).
One piece of advice, maybe: please don’t use this as the general background for your web designs, unless it’s toned down somehow. Moderation usually bodes well :-).