retina.js has a bug (which has a few issues and pull requests filed)

where any images not currently displayed (either through display: none on

the image or on a parent) will end up with a width and height of 0.
The solution appears to be to use the naturalWidth and naturalHeight

properties instead of offsetWidth and offsetHeight. Others have deployed

this without problems, and it works for the cases I've hit as well.
The problem is that we now have to maintain this, but hopefully the next

time retina.js puts out a release, it'll include a fix.

Hit this issue with the new change description stuff. Any file attachments

shown on a collapsed box ended up with a 0 width and height.
After this fix, I could see the images, and they had a correct width and height.