This could be a resource saver and page load optimizer. http://adaptive-images.com/
From what i see, the good thing is it doesnt entirely depend on javascript.

I think we should make it into a plugin - i could.

Anyway, i want to get your ideas on this one, and one question:

How can i edit .htaccess via b2 ? (The scripts needs a few lines in .htaccess to work)