Examples of those necessary images? A few MB is a lot unless you are talking about an artist's portfolio.
http://www.sorryana.rocks/mavericks-wallpaper/
(which loads some content/initial display pretty fast, btw) -- even a full-screen image intended for the Apple Retina iMac is "just" ~3MB. And if you're going to fill the entire viewport (and then some) -- you'll not be needing a lot of other images...