For ScreenBlur, pattern images are PNG images that the program colorizes before
using them as background images. You can modify or add you own pattern images.

Pattern images must be in PNG format but can have any size (and transparency).
Their pixels will be colorized using the color set for Effect in ScreenBlur.
ScreenBlur's Background Image Layout is automatically set to Tile for this images.
Pattern image names must be prefixed with a period to help ScreenBlur recognize them.