Since the great HTTPS switchover, I'm getting a "Parts of this page are not secure (such as images)" warning when viewing the main Photo SE site (Firefox 45.9.0 on Debian, in case it matters). I'm pretty sure that this is due to the weekly featured image link, which link looks to be HTTP rather than HTTPS. (In particular, I don't get the warning on any other SE site or on Photo Meta).
Is it possible to change the image link over to HTTPS? It certainly seems that Imgur serves up the image happily over HTTPS.