Although img@srcset supports the resolution matching use case in a limited way, it does not fully support the art direction use case. To support the the art direction use case, there needs to be some mechanism in place to force the browser to display a given image when condition is met. This is akin to the use case for CSS's !important rule.
(See: http://blog.cloudfour.com/a-framework-for-discussing-responsive-images-solutions/ )
For detailed description of use case, see also: http://usecases.responsiveimages.org/#art-direction
Commenting per the HTML WG’s request:
This bug would be addressed by the proposed `picture` extension specification: See: http://picture.responsiveimages.org/#relationship-to-srcset
Further discussion is available in the WHATWG clone of this bug: https://www.w3.org/Bugs/Public/show_bug.cgi?id=20209
I think it would be a mistake to provide a mechanism "to force the browser to display a given image when condition is met."