If your argument is "byte size", images matter. There's no getting away from that.

This Marco Polo, Columbus-esc view of "rediscovering the basics" is on ego, not efficiency. You're not discovering new territory by rebuilding the wheel, passing it off as "efficiency".

Bandwidth costs would be the only point I could possibly side with - but as mentioned, you add a JPG or any resource for that matter, and the benefits are gone.

If you are going to go about the busy work of rebuilding the wheel, ask yourself, is there a single user's life you are improving? If you have sacrificed the user experience at all - to save 10kb - then you've disserviced them, while patting yourself on the back needlessly. 10k barely changed my experience on a 14.4-33.6kb modem, so I am unsure of how to make the argument today.