I suppose it’s a pattern. Try that:
Go to File -> New : 3×3 with transparent background. Zoom in @ 2970% by using the zoom tool. Take the pencil tool,choose the color you want and create a line in the middle like so:
Go to Edit -> Define Pattern , give it a name and click OK. No open the image you want to apply the pattern,go to the image’s Layer Styles and choose Pattern Overlay. Now pick the pattern you created and you should be ok.
Hope that helps 
