Maybe another app has taken over your JPEGs that you installed, unrelated to permissions. I can open the image in Preview. I've been having a lot of permission issues lately, I hate the new disk utility. It's no longer necessary to verify or repair permissions with Disk Utility. http://vicnot.net/el-capitan/mac-os-x-repair-disk-permissions-not-working.html
I'm gob-smacked that the tool remains on disk - it seems an admission of failure, since SIP is supposed to mean "nothing can go wrong" in this space. Mac OS X 10.3 or earlier: Choose Installer > Disk Utility in the menu bar. 1.4. Disk Utility cannot repair the disk If the Repair Disk function of Disk Utility found directory corruption that it could not repair: If Disk Utility returns the message "Underlying task reported Because differing permissions on files or folders, either with or without consequences, is nearly guaranteed to happen over time when using a Mac and installing and uninstalling a variety of applications, click to read more
This limitation of the Repair Disk Permissions function has been debated around the Web, but you can confirm it yourself with a bit of Terminal savvy: By using the fs_usage command Restart your computer and re-launch the product. Background pic disappeared. Reply Phil H.