1. First we are going to make the pattern.
Create a new document 4 x 4 pixels with transparent background. Zoom in to max (1600%) and make a pattern simular to mine. Use a 1 pixel brush for this.
Now select all Select > All (Ctrl+A) and go to Edit > Define Pattern, name the pattern and click ok.
2. Now create a new document 4 x 4 pixels with white background. Create a new layer and fill it with the pattern you just made.
3. Lower the opacity to 10% and your background pattern are finished. Try with other colors on background as well.
More Tutorials: 
