As it was pointed out[↗] on the French site, the images can be incorporated directly in the question. That is, just add images to the question in the standard way, then edit the HTML code to place the URL of the images in the JavaScript code.
The marker made invisible is at the top left of the image. If necessary, it could be moved to the center of the image, but the JavaScript code will become a bit more complicated. In most cases, the marker at the top left of the image should be fine. Do not hesitate to report a contrary case.