I booted the F26 20160401.n.0 MATE-Compiz live image (the most recent at time of filing bug). The desktop background is a simple blue-green gradient, not the Fedora 26 background (a sort of watercolor-style painted rural landscape in light blue, black and white). The login manager (not sure which one is actually used) does use the Fedora 26 background.
mate-desktop-1.18.0-2.fc26 has been submitted as an update to Fedora 26. https://bodhi.fedoraproject.org/updates/FEDORA-2017-28e51a333c
(In reply to Adam Williamson from comment #0) > I booted the F26 20160401.n.0 MATE-Compiz live image (the most recent at > time of filing bug). The desktop background is a simple blue-green gradient, > not the Fedora 26 background (a sort of watercolor-style painted rural > landscape in light blue, black and white). First i thought the new default wallpaper was a mistake, but it seems to be only a bad joke. The worse fedora wallpaper ever....
mate-desktop-1.18.0-2.fc26 has been pushed to the Fedora 26 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2017-28e51a333c
mate-desktop-1.18.0-2.fc26 has been pushed to the Fedora 26 stable repository. If problems still persist, please make note of it in this bug report.