This is meant as a meta-bug to improve the information provided for responsive images.

Miriam already mentioned several pieces of information relevant to developers in bug 1260230 comment 3. I've included some additional points:

• Show the currently active image source
• Show all dimensions of the image, i.e. intrinsic size/source size, natural size/density-corrected size (maybe including the current pixel density), and layout size
• Show the currently active size of the sizes attribute
• Clarify if an image is being used from cache, and what image would be used otherwise (maybe with toggling)
• Respond dynamically to resizing

Sebastian