This is dependant on the previous option. If you don't checked "Skip all images", then you can set if the images found are going to be used as background or not.
When you tick this option, the images used in the window are printed exactly where they are.
See the examples String and prompts with graphics, no tabs and String and prompts with graphics and tabs.
If you don't tick this option, and images are present on the window, it is assumed that there is only one image per Tab on the window, and that image is the background for the input of data (mimicking a paper Form). The report will change it size according to the size of this one image. There can be a different background image per Tab on the window, but the template can't pocess more than one image by Tab.
Since this is a global setup, all your windows will take this option unless overrided locally.