I’ve been following the RICG for a while now and there isn’t much I can add to what other members have said here. Personally I think it’s understandable to suggest some of the solutions that only when looked at in more detail don’t seem possible.

I do think a responsive image format is the best solution, but for reasons pointed out above, it probably won’t happen, therefore we need a different solution and this has proved quite difficult to conjure up. I think the two solutions being looked at currently are the best we have, they solve the “art direction” issue well, which I think don’t think is a design/style issue as much as it a contextual one. Any images that can be changed via CSS without impacting context would most often be a background image anyway in my opinion.

The point about considering where we need images is a good one I think and ties into an attitude that I think exists with some designers/devs that media queries = responsive when in fact it is decisions like this that should all feed into the a responsive design. There is a good article about this on A List Apart if anyone fancies a read http://www.alistapart.com/articles/the-web-aesthetic/