Reassigning the bug to metapackage since fixing it requires upgrading of both mate-desktop (to 1.16.2) and Caja (to 1.16.3). Also merged all the duplicate reports since they're all about the same regression.
Actually, it's recommended to upgrade Caja to the latest 1.16.x version which is currently 1.16.6, as this would fix some other bugs reported here. I would not recommend opting for a later stable release patch, as the amount of code changes is quite big (even for the desktop background fix alone, not counting other included bugfixes). There's not much time left really, as Stretch is scheduled for release on June 17th, and June 9th is set as the deadline for any changes: https://lists.debian.org/debian-devel-announce/2017/05/msg00002.html
