Tried with F29217 in Chrome 39 / Ubuntu:
{F29217}
* click in the image
* click on the download link
* press Ctrl-S
* I get a 403 with "File Link Has Expired"
Apparently Phabricator uses some weird one-time-link scheme. Google Chrome, for whatever reasons, tries to redownload the file when I tell it to save to the disk, instead of just saving the already displayed image. (I suspected "disable cache" option in devtools which can cause similar issues, but it is off.)
The installation at secure.phabricator.com behaves saner in multipleaspects:
* file links are not one-time (compare middle-clicking this image and reloading with doing the same for https://secure.phabricator.com/T6964 )
* clicking on the "Download" button actually downloads the file, while on the WMF instance it just opens it. The download link has `?download=1` in both cases, so I suspect this is a webserver configuration issue.
Both instances set a past Expires header on the file, which is probably the "whatever reason" mentioned above.