20141125 is the last day we have images/, LiveOS/ and similar directories:
http://koji.fedoraproject.org/mash/branched-20141125/21/x86_64/os/

After that, only Packages/ and repodata/ are available:
http://koji.fedoraproject.org/mash/branched-20141127/21/x86_64/os/

The log says:
{{{
yum.verbose.YumBase.INFO_2: Running Transaction Check
pylorax.ltmpl.ERROR: template command error in runtime-install.tmpl:
pylorax.ltmpl.ERROR: run_pkg_transaction
pylorax.ltmpl.ERROR: YumRPMCheckError: [u'ERROR with transaction check vs depsolve:', 'fedora-productimg-cloud conflicts with fedora-productimg-workstation-21-6.fc21.noarch', 'fedora-productimg-server conflicts with fedora-productimg-workstation-21-6.fc21.noarch', 'fedora-productimg-server conflicts with fedora-productimg-cloud-21-6.fc21.noarch', 'fedora-productimg-workstation conflicts with fedora-productimg-cloud-21-6.fc21.noarch', 'fedora-productimg-cloud conflicts with fedora-productimg-server-21-6.fc21.noarch', 'fedora-productimg-workstation conflicts with fedora-productimg-server-21-6.fc21.noarch']
pylorax.ltmpl.DEBUG: Traceback (most recent call last):
pylorax.ltmpl.DEBUG: File "/usr/lib/python2.7/site-packages/pylorax/ltmpl.py", line 508, in run_pkg_transaction
pylorax.ltmpl.DEBUG: rpmDisplay=LoraxRpmCallback())
pylorax.ltmpl.DEBUG: File "/usr/lib/python2.7/site-packages/yum/init.py", line 6469, in processTransaction
pylorax.ltmpl.DEBUG: self._doTestTransaction(callback,display=rpmTestDisplay)
pylorax.ltmpl.DEBUG: File "/usr/lib/python2.7/site-packages/yum/init.py", line 6548, in _doTestTransaction
pylorax.ltmpl.DEBUG: raise Errors.YumRPMCheckError,retmsgs
pylorax.ltmpl.DEBUG: YumRPMCheckError: [u'ERROR with transaction check vs depsolve:', 'fedora-productimg-cloud conflicts with fedora-productimg-workstation-21-6.fc21.noarch', 'fedora-productimg-server conflicts with fedora-productimg-workstation-21-6.fc21.noarch', 'fedora-productimg-server conflicts with fedora-productimg-cloud-21-6.fc21.noarch', 'fedora-productimg-workstation conflicts with fedora-productimg-cloud-21-6.fc21.noarch', 'fedora-productimg-cloud conflicts with fedora-productimg-server-21-6.fc21.noarch', 'fedora-productimg-workstation conflicts with fedora-productimg-server-21-6.fc21.noarch']
}}}
http://koji.fedoraproject.org/mash/branched-20141127/logs/x86_64.log

I'm not sure whether this affects our ability to create a full Fedora 21 release compose?