Upon using dCore-stretch I noticed there is no support for viewing JPEG images in any image viewer. Debian has removed some libjpeg packges since Jessie. The current libjpeg* packages available in Stretch seem not to support viewing JPEG images, and I have imported and tried them all. I have uploaded a libjpeg-turbo8-stretch package to the prebuilt section which allows JPEG images to be viewed as in other dCore ports. The source tarball is hosted here on our server. This is a workaround, and as this is still fairly deep in the testing stage of Stretch, so I am sure a solution will be found before release.