TV Lines
First load up a picture, or use the picture below:
Right click on this picture and "Save picture as"
To save this picture, Right click on it then save as....
Create a new image 4 pixels wide 2 by pixels high. Then zoom in as large as possible  using the zoom tool or the navigator.
After zoom in, you can see clearly...
Before zoom in, too small, you can't see...
Use the pencil tool to draw a black line, your brush must be 1 pixels only:
Go to Select>All, then Edit>Define Pattern. Ok, you can close it now.
(The pattern is defined)

Go back to the picture you saved just now, make a new layer, then go to
Now you can see some TV lines, but it is too dark, so  choose "Overlay" from the pop down menu in the layers tab.