[Gaussian]

Ok, I got it Lee. There's pinstriped light, medium and dark gray. I assume looking at your screenshot that you want dark gray.

- Open a new document, size 1 by 2 pixels.
- Zoom in to 1600%
- Select the pencil tool, brush size 1 pixel
- Set foreground color to 191919
- Add top pixel with pencil tool
- Set foreground color to 3f3f3f
- Add bottom pixel with pencil tool
- Select All (on Mac is Command + A)
- Menu: edit/define pattern... and name it Dark Gray Pinstriped and click OK

Now when you need the Lightroom background all you need to do is fill the preferred area with the Paint Bucket tool with pattern selected in the option bar and using your Dark Gray Pinstriped pattern (you can select it when you click on the black triangle marked with the red arrow).