*DavidSparks*: Yeah, I’m not 100% married to “picture,” to represent the new element. “Poster” would make more sense, but it’s a term already in use and that might trip people up. Maybe “art?” Stuff we can nail down once we have something working, I figure.
In terms of the media attributes, you could still specify media=“screen” and the like in there—you can use any combination of media queries, the same as you would in your CSS. I like it because it paves the way for exactly the kind of conversation you’re mentioning: as media queries change and adapt over time, so too can this new element.
And the best part is that the HTML5 dictates that sources that don’t match the media attribute are never requested. If implemented correctly, it does exactly what you’ve said: grab the source we want, and bypass all the rest.