Multiple Base64 images on Html page and smooth loading

Does someone know a technique to make asynchonous image parsing when multiple images are printed (base64) on a webpage ?

It causes Firefox to have small freeze on loading/parsing on a gaming machine (for more than 15 images 1.5MB), so I'm a bit worried of that.

Still I think giving an url and using a javascript async (lazy) image loading is better, if someone have some more informations tips, I'll be glad to hear it Thanks.