Are you sure you're actually clicking the images first, so they're brought up in the image viewer box with the other options available, and then right-clicking -> View Image/Open Image/whatever?
If you are, then that's very strange, and I have no idea why that's happening for you and not for anybody else. What browser and OS are you using?
> It is too slow to load many such large images automatically.
The images don't all load automatically, though; an image only begins to load when you click on it individually, opening it within the viewer, on a Google Images results page.
Here[0] is a screenshot example. Clicking on 'Open image in new tab' (or 'View Image' in Firefox) will open the image[1] directly, and inspecting the page's source will reveal it is simply an <img> element with the URL as the src value. The size ought to make no difference; I tried up to 10 MP.
It may take a second to load, but that's how Google Images works: once an image is open in the viewer, it is quite literally just embedding the unadulterated source image within the page. It has been this way since at least 2010.
(Unless, of course, there is behaviour unique to Safari or OS X: of that I have no idea.)
