Inner content should not be rendered by clients supporting the picture tag. This allows for a natural fallback without using , like we already have for canvas.I'm not a great fan of "picture" either. We already have . Why not ?
The ideal solution IMO would be something like Progressive JPEG (with less artifacts): you serve a single high-quality image, and the browser downloads as much of it as it sees fit for the situation. Smaller images would be created from a large, lower quality download.