comparison

<picture>
  <source media="(min-width: 800px)" srcset="pic-big.jpg 1x, pic-big-hd.jpg 2x">
  <source media="(min-width: 400px)" srcset="pic-med.jpg 1x, pic-med-hd.jpg 2x">
  <img src="small.jpg" alt="…">
</picture>

<img
  src-2="(min-width: 400px) pic-med.jpg 1x, pic-med-hd.jpg 2x"
  src-1="(min-width: 800px) pic-big.jpg 1x, pic-big-hd.jpg 2x"
  src="small.jpg"
  alt="…">

Suppose each image file has different content because of art direction — for example, the three images in this CSS Tricks article under the heading "Do I care about art direction?". If the change is drastic enough, you might need different alt values depending on which image has loaded.

Have you considering allowing for, er, alternate alt and title values?

@patik, if the change is that drastic, then the developer is doing img wrong.

@patik, to be clear, we don't want to introduce something new that would allow the developer to do what you describe.