The script timelessCreateEmptyImage does exactly what its name says: It creates an empty image (which is a black image with minimum intensity = maximum intensity = 0). Possible applications for empty images are:

• Replacing an image which is not usable because of shadow/double diffraction/diamond spots (because the data processing doesn't work when there's a gap in the set of images). See here for more info on when to use this.
• Replacing an image which was lost during processing or data transfer (because the data processing doesn't work when there's a gap in the set of images)
• Weakening the intensity of another image by calculating the average of that image and an empty image (rarely used)

However, the empty image is not created from scratch. One has to provide another image which serves as a basis. First, the basis image is copied so the original is not erased. Then, the size and the amount of pixels from the basis image is kept and the intensity is set to zero.