Since you have PS and Gimp then here's how I do it:
1. decide how much distance you want each and every single pixel to represent, say like 1 pixel = 2 miles
2. make a rectangle that is 10 pixels wide (or 20 or 30 just something based on 10) and make it half as tall; so 5 in my example...this will be a 10 pixel rectangle that represents 20 miles
3. duplicate that layer and hit ctrl-i to invert the color
4. hit the arrow key 10 times to move the new rectangle over (or hold down the shift key and hit the arrow once)
5. when lined up then merge down
6. duplicate, move, merge, and repeat until you fill up the screen with one long line across (doesn't take all that long really)
7. duplicate the long line and move it to the top, move the other to the bottom
8. duplicate one line, rotate 90 degrees, and move it to one side edge
9. duplicate and move it to the other side
10. when all done merge together
11. not really a step, just a note...by making my rectangle 5 by 10 then they meet at the corners very well and if you use some other tallness then you have to tweak the corners a bit
12. (the step folks forget about) not totally necessary but sometimes it is; because you have the two vertical lines parts will be hanging out there in space where you can't see them (off of the canvas) but they're still there so if your pc is chugging along or your layer styles seem weird then crop them out...ctrl-click on a layer that is filled full (like the background layer or the paper layer or whatever) then hit edit-crop on the layer with the lines.
This is for basic black and white rectangles, once you learn the technique then you can go back and add a stroke around the rectangles or whatever fancy thing you want. I don't use a pattern as it doesn't align properly most of the time and if you use a small pattern and want to scale up the size it will sometimes get blurred.