I am using the League theme as a template for an elearning project. I replaced the theme images with my own using (Change image), but when I Preview the project in the browser (Safari) this is what some of the images look like.
Lack of resources is often the problem if you see red rectangles replacing the image.
Does the image have exactly the size you needed in Captivate? Was screenshot after publishing and uploading to a webserver, or is it with Preview HTML in Browser? Did you only try Safari (not the best choice)? PNG images need JSON installed on the webserver.
I already answered a question about the League QSP somewhere, was that you as well? Which slide did you use here?