I suspect there's not much to gain by caching images in the browser: If you're looking at a page full of comments with hundreds of avatars, chances are the next page is going to make you load hundreds more that you haven't seen already: There is a very large number of commenters, and you probably won't see the same people on every page.

The demo is right: they ask for 300 different images (as in, different URLs), and their packager makes it faster.

Also, how would you inline include images? Using base 64 in the image tag?