Not sure if this has been asked before - couldn't find anything on the subject.
Is there a way of adding some soft of place holder to an image to set it's size (even though its responsive) while its loading to prevent the page jumping all over the place as images load?
Is the image really large in size? If so, you might want to load smaller images for mobile devices. A mobile phone sized image should not take so long to download that it causes a noticeable delay in page load speed.